JPH1093192A - Gallium nitride based compound semiconductor laser and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently perform carrier injection into an active layer, suppress a voltage drop at an electrode contact or the like, operate at a low threshold and a low voltage, and achieve high reliability. To achieve. SOLUTION: The gallium nitride based compound semiconductor laser is
An active layer 14 is formed on a sapphire substrate 10
It has a double hetero junction structure sandwiched between 3 and 15. p-
G having a stripe-shaped opening on the cladding layer 15
An aN current block layer 16 is formed. Further, a current is injected into the opening of the current blocking layer 16, and the buried layer 17 of p-GaN and the contact layer 1 having a larger area than the opening are formed.
8 are formed. The active layer 14 has a band gap energy, and has a multiple quantum well (MQW) structure including a periodic structure formed by repeating two types of InGaAlN layers each having a thickness of 10 nm or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device using a gallium nitride-based compound semiconductor and a manufacturing technique, and more particularly to a gallium nitride-based compound semiconductor laser and a manufacturing method thereof.
Further, the present invention relates to a method for manufacturing a gallium nitride-based compound semiconductor device.

[0002]

2. Description of the Related Art In recent years, GaN, InGaN, GaAl
Gallium nitride-based compound semiconductors such as N and InGaAlN have attracted attention as materials for blue semiconductor lasers. Semiconductor lasers made of these materials can be narrowed down to a small beam by shortening the wavelength, and are expected as light sources for high-density information processing such as optical disks.

[0003] Various structures and manufacturing methods have been proposed for this type of semiconductor laser, but satisfactory characteristics have not been obtained in any case due to the difficulty of crystal growth of the gallium nitride-based compound semiconductor layer. That is, even if a gallium nitride-based compound semiconductor layer is grown as a crystal, good quality crystals cannot be obtained, and carrier injection into the active layer cannot be performed efficiently due to poor crystal quality. Further, in a structure having a stripe opening in the current block layer, the crystal quality of the regrown layer after the etching for forming the stripe opening is deteriorated, which causes a voltage drop at an electrode contact or the like. As described above, conventionally, in order to realize a blue semiconductor laser that operates at a low threshold value and a low voltage and has high reliability for practical use to an optical disk or the like, it is necessary to efficiently perform carrier injection into the active layer. It is important to suppress the voltage drop at the electrode contacts and the like, but at present, a configuration that satisfies these requirements has not yet been obtained.

[0004]

In a semiconductor laser using a gallium nitride-based compound semiconductor, it is difficult to obtain a high-quality crystal layer due to the difficulty of crystal growth of the material, and etching for forming a stripe opening is performed. The crystal quality of the later regrown layer is further reduced. As a result, carriers cannot be efficiently injected into the active layer, and a voltage drop occurs at an electrode contact or the like. It has been difficult to realize an element having the following.

[0005] Further, the point that regrowth after once etching the gallium nitride-based compound semiconductor layer cannot be performed well is not limited to the semiconductor laser, but similarly applies to various semiconductor devices using the gallium nitride-based compound semiconductor. I can say that.

The present invention has been made in view of the above circumstances, and has as its object to efficiently inject carriers into an active layer and to suppress a voltage drop at an electrode contact or the like. It is an object of the present invention to provide a gallium nitride-based compound semiconductor laser which can be operated at a low threshold voltage and a low voltage and has high reliability for practical use in optical disks and the like, and a method for manufacturing the same.

Another object of the present invention is to provide a gallium nitride-based compound semiconductor that can favorably perform regrowth after once etching a gallium nitride-based compound semiconductor layer and can contribute to the improvement of characteristics of various semiconductor devices. An object of the present invention is to provide a method for manufacturing a device.

[0008]

SUMMARY OF THE INVENTION A first aspect of the present invention is as follows.
In a gallium nitride-based compound semiconductor laser, an active layer having a periodic structure formed by repeating two or more kinds of semiconductor layers, and an active layer disposed to sandwich the active layer so as to form a double heterojunction structure. First and second cladding layers of first and second conductivity types, first and second electrodes connected to the first and second cladding layers, between the second electrode and the second cladding layer, A current block layer having a stripe-shaped opening for confining a current to the double hetero junction structure; and a current block layer disposed between the second electrode and the current block layer and in the opening. A current injection layer having a larger area than the opening,
The active layer, said first and second cladding layers, the current blocking layer, and each of the current injection layer are that consists essentially of a material represented by the following composition _{formula, In x Ga y Al z N} , Where x + y + z = 1, 0 ≦
x, y, z ≦ 1 When the thickness of the current blocking layer is TA and the distance between the current blocking layer and the active layer is TB, TB <TA
Satisfying the condition (1).

A second aspect of the present invention is a gallium nitride-based compound semiconductor laser according to the first aspect, wherein 2TB <TA.
Characterized by satisfying the following condition:

A third aspect of the present invention is a gallium nitride based compound semiconductor laser according to the second aspect, wherein 2TB <TA.
It is characterized by satisfying the condition of <10 TB.

According to a fourth aspect of the present invention, in the gallium nitride based compound semiconductor laser according to the first aspect, when the thickness of the current injection layer excluding the inside of the opening is TC, TC <T
The condition of A is satisfied.

According to a fifth aspect of the present invention, in the gallium nitride-based compound semiconductor laser according to the first aspect, when the thickness of the current injection layer excluding the inside of the opening is TC, TB <T.
C is satisfied.

According to a sixth aspect of the present invention, in the gallium nitride-based compound semiconductor laser according to the first aspect, the current blocking layer contains a doped second conductivity type impurity.

According to a seventh aspect of the present invention, in the gallium nitride-based compound semiconductor laser according to the first aspect, a side wall of the opening and an interface between the current blocking layer and the current injection layer are at an angle of 45 °. It is characterized by forming an angle of 90 °.

According to an eighth aspect of the present invention, there is provided a gallium nitride-based compound semiconductor laser in which a double heterojunction structure and an active layer having a periodic structure formed by repeating two or more types of semiconductor layers are formed. First and second conductive type first and second conductive types, respectively, disposed with an active layer interposed therebetween.
A cladding layer, first and second electrodes connected to the first and second cladding layers, and a current flowing between the second electrode and the second cladding layer for the double hetero junction structure. A current blocking layer having a stripe-shaped opening for constricting; and a current injection layer disposed between the second electrode and the current blocking layer and in the opening, and having a larger area than the opening. , the active layer, said first and second cladding layers, the current blocking layer, and each of the current injection layer are that consists essentially of a material represented by the following composition formula, in _x Ga _y Al _z N , Where x + y + z = 1, 0 ≦
x, y, z ≦ 1 When the thickness of the current blocking layer is TA and the thickness of the current injection layer excluding the inside of the opening is TC, the condition of TC <TA is satisfied. It is characterized by.

According to a ninth aspect of the present invention, in the gallium nitride based compound semiconductor laser according to the eighth aspect, a stripe-shaped V-shaped groove is formed on the surface of the current injection layer above the opening. The second electrode may have a portion in the groove that contacts the current injection layer.

According to a tenth aspect of the present invention, in the gallium nitride compound semiconductor laser according to the ninth aspect, the depth of the opening is d1, and the widths of the upper and lower portions of the opening are W1 and W2, respectively. Hour, 24 <(W1 + W2) × d1 /
It is characterized by satisfying the condition of TC.

According to an eleventh aspect of the present invention, there is provided a gallium nitride based compound semiconductor laser in which a double heterojunction structure and an active layer having a periodic structure formed by repeating two or more types of semiconductor layers are formed. First and second cladding layers of first and second conductivity types, respectively, disposed between the active layer, first and second electrodes connected to the first and second cladding layers, A current blocking layer disposed between the two electrodes and the second cladding layer, the current blocking layer having a stripe-shaped opening for narrowing a current to the double hetero junction structure; and the second electrode and the current blocking layer. And an active layer, the first and second cladding layers, a current blocking layer, and a current injection layer, each of which has a larger area than the opening, and a current injection layer having the following composition formula: Represented by And it consists essentially of that _{material, In x Ga y Al z N} , wherein x + y + z = 1,0 ≦
x, y, z ≦ 1 The distance between the current blocking layer and the active layer is represented by TB,
When the thickness of the current injection layer excluding the inside of the opening is TC, the condition of TB <TC is satisfied.

According to a twelfth aspect of the present invention, in a gallium nitride compound semiconductor laser, an active layer having a periodic structure formed by repeating two or more types of semiconductor layers and a double heterojunction structure are formed. First and second cladding layers of first and second conductivity types, respectively, disposed between the active layer, first and second electrodes connected to the first and second cladding layers, A current blocking layer disposed between the two electrodes and the second cladding layer, the current blocking layer having a stripe-shaped opening for narrowing a current to the double hetero junction structure; and the second electrode and the current blocking layer. A current injection layer disposed between and in the opening, and having a larger area than the opening, and each of the active layer, the first and second cladding layers, the current blocking layer, and the current injection layer, under And it consists essentially of a material represented by the composition _{formula, In x Ga y Al z N} , wherein x + y + z = 1,0 ≦
x, y, z ≦ 1 The portion of the current injection layer adjacent to the active layer has a band gap larger than a band gap corresponding to an emission wavelength of the active layer and has a larger refractive index than the current blocking layer. And that it comprises.

A thirteenth aspect of the present invention is the gallium nitride-based compound semiconductor laser according to the twelfth aspect, wherein
The cladding layer and the current blocking layer have substantially the same refractive index.

According to a fourteenth aspect of the present invention, in the gallium nitride compound semiconductor laser according to the twelfth aspect, a portion of the current injection layer adjacent to the active layer and the second cladding layer have substantially the same refractive index. It is characterized by having.

According to a fifteenth aspect of the present invention, in a gallium nitride compound semiconductor laser, an active layer having a periodic structure formed by repeating two or more types of semiconductor layers and a double heterojunction structure are formed. First and second cladding layers of first and second conductivity types, respectively, disposed between the active layer, first and second electrodes connected to the first and second cladding layers, A current blocking layer disposed between the two electrodes and the second cladding layer, the current blocking layer having a stripe-shaped opening for narrowing a current to the double hetero junction structure; and the second electrode and the current blocking layer. A current injection layer disposed between and in the opening, and having a larger area than the opening, and each of the active layer, the first and second cladding layers, the current blocking layer, and the current injection layer, under And it consists essentially of a material represented by the composition _{formula, In x Ga y Al z N} , wherein x + y + z = 1,0 ≦
x, y, z ≦ 1 The current blocking layer has a band gap larger than a band gap corresponding to an emission wavelength of the active layer, and has a larger refractive index than a portion of the current injection layer adjacent to the active layer. And that it comprises.

According to a sixteenth aspect of the present invention, in a gallium nitride compound semiconductor laser, an active layer having a periodic structure formed by repeating two or more types of semiconductor layers and a double heterojunction structure are formed. First and second cladding layers of first and second conductivity types, respectively, disposed between the active layer, first and second electrodes connected to the first and second cladding layers, A current blocking layer disposed between the two electrodes and the second cladding layer, the current blocking layer having a stripe-shaped opening for narrowing a current to the double hetero junction structure; and the second electrode and the current blocking layer. A current injection layer disposed between and in the opening, and having a larger area than the opening, and each of the active layer, the first and second cladding layers, the current blocking layer, and the current injection layer, under And it consists essentially of a material represented by the composition _{formula, In x Ga y Al z N} , wherein x + y + z = 1,0 ≦
x, y, z ≦ 1 A portion of the current injection layer adjacent to the active layer has a band gap larger than a band gap corresponding to an emission wavelength of the active layer, and the current blocking layer includes:
Having a band gap smaller than the band gap corresponding to the emission wavelength of the active layer.

According to a seventeenth aspect of the present invention, there is provided a gallium nitride based compound semiconductor laser which forms an active layer having a periodic structure formed by repeating two or more types of semiconductor layers and a double heterojunction structure. First and second cladding layers of first and second conductivity types, respectively, disposed between the active layer, first and second electrodes connected to the first and second cladding layers, A current blocking layer disposed between the two electrodes and the second cladding layer, the current blocking layer having a stripe-shaped opening for narrowing a current to the double hetero junction structure; and the second electrode and the current blocking layer. A current injection layer disposed between and in the opening, and having a larger area than the opening, and each of the active layer, the first and second cladding layers, the current blocking layer, and the current injection layer, under And it consists essentially of a material represented by the composition _{formula, In x Ga y Al z N} , wherein x + y + z = 1,0 ≦
x, y, z ≦ 1 A stripe-shaped groove continuous with the opening is formed on the surface of the second cladding layer, and the current injection layer is disposed in the groove so as to be in contact with the second cladding layer. To be performed.

An eighteenth aspect of the present invention is directed to an active layer and first and second conductive type first and second conductive types, respectively, which are disposed with the active layer interposed therebetween so as to form a double heterojunction structure. A cladding layer, first and second electrodes connected to the first and second cladding layers, and a current flowing between the second electrode and the second cladding layer for the double hetero junction structure. A current blocking layer having a stripe-shaped opening for constricting; and a current injection layer disposed between the second electrode and the current blocking layer and in the opening, and having a larger area than the opening. , the active layer, said first and second cladding layers, the current blocking layer, and each of the current injection layer are that consists essentially of a material represented by the following composition formula, in _x Ga _y Al _z N , Where x + y + z = 1, 0 ≦
A method for manufacturing a gallium nitride based compound semiconductor laser having x, y, z ≦ 1, wherein a step of forming a laminated film having the double heterostructure on a supporting substrate, and a step of forming the current blocking layer on the laminated film Laminating a surface protection layer and a surface protection layer; etching a part of the surface protection layer and the current block layer to form the stripe-shaped opening; leaving the surface protection layer at a high temperature in a gas phase Forming the current injection layer in the opening and on the current block layer after the crystal is removed by re-evaporation of the crystal.

A nineteenth aspect of the present invention is directed to an active layer and first and second conductive type first and second conductive types, respectively, which are disposed with the active layer interposed therebetween so as to form a double heterojunction structure. A cladding layer, first and second electrodes connected to the first and second cladding layers, and a current flowing between the second electrode and the second cladding layer for the double hetero junction structure. A current blocking layer having a stripe-shaped opening for constricting; and a current injection layer disposed between the second electrode and the current blocking layer and in the opening, and having a larger area than the opening. , the active layer, said first and second cladding layers, the current blocking layer, and each of the current injection layer are that consists essentially of a material represented by the following composition formula, in _x Ga _y Al _z N , Where x + y + z = 1, 0 ≦
A method for manufacturing a gallium nitride based compound semiconductor laser having x, y, z ≦ 1, wherein a step of forming a laminated film having the double heterostructure on a supporting substrate, and a step of forming the current blocking layer on the laminated film Forming, forming a stripe-shaped opening by dry-etching a part of the current block layer, and heating the support substrate, the laminated film, and the current block layer to 100 ° C. or more. HNO ₃ : HC
forming the current injection layer in the opening and on the current block layer after being immersed in a solution of l = 3: 1;
It is characterized by having.

A twentieth aspect of the present invention relates to an active layer and first and second conductive type first and second conductive types, respectively, which are disposed with the active layer interposed therebetween so as to form a double heterojunction structure. A cladding layer, first and second electrodes connected to the first and second cladding layers, and a current flowing between the second electrode and the second cladding layer for the double hetero junction structure. A current blocking layer having a stripe-shaped opening for constricting; and a current injection layer disposed between the second electrode and the current blocking layer and in the opening, and having a larger area than the opening. , the active layer, said first and second cladding layers, the current blocking layer, and each of the current injection layer are that consists essentially of a material represented by the following composition formula, in _x Ga _y Al _z N , Where x + y + z = 1, 0 ≦
A method for manufacturing a gallium nitride based compound semiconductor laser having x, y, z ≦ 1, wherein a step of forming a laminated film having the double heterostructure on a supporting substrate, and a step of forming the current injection layer on the laminated film Forming a current blocking layer having a stripe-shaped opening by partially introducing an impurity into a selected layer comprising one or both of the second cladding layer and the current injection layer. And a step of performing

According to a twenty-first aspect of the present invention, in the method for manufacturing a gallium nitride based compound semiconductor laser according to the twentieth aspect, the selected layer contains one or both of Mg and Al, and the impurity is O. It is characterized by being.

[0029]

FIG. 1 is a sectional view showing an element structure of a gallium nitride based compound semiconductor laser according to an embodiment of the present invention. In the following description, portions having substantially the same functions and configurations are denoted by the same reference numerals, and repeated description will be made as necessary.

On a sapphire substrate 10, a GaN buffer layer 11, a Si-doped GaN n-contact layer 12,
Si-doped GaAlN n-clad layer 13, MQW active layer 14, Mg-doped GaAlN p-clad layer 1
5. A non-doped GaN current blocking layer 16 is laminated, and the current blocking layer 16 is etched in a stripe shape. The active layer 14 has two types of In having different band gap energies and each having a thickness of 10 nm or less.
It has a multiple quantum well (MQW) structure composed of a periodic structure formed by repeating GaAlN layers.

On the p-cladding layer 15 and the current block layer 16 exposed by the etching of the current block layer 16, a p-buried layer 17 of Mg-doped GaN and a p-contact layer 18 of Mg-doped GaN are laminated. And
The n-side electrode 21 is formed on the exposed surface of the n-contact layer 12 while being partially etched from the p-contact layer 18 to the middle of the n-contact layer 12, and the p-side electrode 21 is formed on the surface of the p-contact layer 18. An electrode 22 is formed.

As described above, in the present embodiment, a periodic structure composed of a repetition of two types of InGaAlN layers having different band energies and each having a thickness of 10 nm or less is used as the MQW active layer 14. Regrowth is performed to form a current confinement structure. For this reason, the crystal defects considered to be generated at the regrowth interface and the regrowth layer are reduced, and a flat regrowth surface is obtained, the contact resistance at the p-side electrode 22 is low, and an element having a low operating voltage can be obtained. It is possible to obtain.

Further, since the crystal defects can be reduced by using the periodic structure, the carriers can be efficiently injected into the active layer 14. Further, the crystal quality of each layer of the element portion can be improved by interposing the buffer layer 11 instead of directly forming each layer required for the element portion on the sapphire substrate 10, thereby also improving the carrier injection. This can contribute to improvement in efficiency and reduction in contact resistance.

Next, a method of manufacturing the gallium nitride compound semiconductor laser shown in FIG. 1 will be described.

First, as shown in FIG. 2A, a metal organic chemical vapor deposition (MOCVD) method is formed on a sapphire substrate 10.
To grow a buffer layer 11 made of GaN, AlN, AlGaN, or the like to a thickness of about 10 to 200 nm, and form an n-contact layer 12 of Si-doped GaN thereon by MOCV.
It is grown to a thickness of 4 μm by Method D. Then, Si-doped G
An n-clad layer 13 of a _0.8 Al _0.2 N is grown to a thickness of 250 nm by MOCVD. Although the growth method is not described below, it is assumed that the MOCVD method is used in all cases.

Next, a non-doped GaN having a thickness of 200 n
m light guide layer, 1.5 nm thick non-doped In _0.25
Ga _0.75 N and non-doped In _0.05 Ga with a thickness of 3 nm
_An MQW active layer 14 is formed by laminating a multiple quantum well (MQW) structure formed by repeating two types of _0.95 N InGaAlN layers for 50 periods, and a 200 nm-thick non-doped GaN optical guide layer.

Next, the p of Mg-doped Ga _0.8 Al _0.2 N
Growing the cladding layer 15 followed by the current blocking layer 16
Is grown to a thickness of 0.6 μm. Further, as the surface protective layer 31, non-doped In _0.15 Ga _0.85
A layer made of N is grown by 0.2 μm. At this time, the surface protective layer 31 is grown at a temperature of 900 ° C. or lower in an atmosphere containing nitrogen gas and ammonia gas as main components.

Next, the wafer is taken out of the growth apparatus, and FIG.
As shown in (b), a part of the surface protection layer 31 and the current block layer 16 is etched into a stripe having a width of 5 μm by reactive ion etching (RIE) to form an opening, and the p-cladding layer 15 is formed. Expose.

Next, the wafer is again put into the growth apparatus and exposed to a temperature higher than 900 ° C. in an atmosphere containing hydrogen gas as a main component in addition to nitrogen gas and ammonia gas, as shown in FIG. Then, the surface protective layer 31 is evaporated to form a clean current blocking layer surface.

Next, as shown in FIG. 3 (a), M is applied on the current blocking layer 16 and the exposed p-cladding layer 15.
0.8 μm thick p-buried layer 17 of g-doped GaN
Then, a p-contact layer 18 of 0.2 μm in thickness of p ⁺ -GaN doped with Mg to a higher concentration than the buried layer 17 is sequentially grown.

Next, the wafer is taken out of the growth apparatus, and FIG.
As shown in FIG. 2B, the n-contact layer 12 where the n-side electrode 21 is to be formed is exposed by partially etching the RIE from the p-contact layer 18 to the middle of the n-contact layer 12.

Next, Ti-A is formed on the n-contact layer 12.
An n-side electrode 21 made of u is formed. A p-side electrode 22 made of Pd-Au is formed on the p-contact layer 18.
The current blocking layer 16 is formed so as to have a wider area including immediately above the stripe-shaped opening. This allows
The structure shown in FIG. 1 is obtained. The p-side electrode 22 may be Pt-Au, Ni-Au, or the like.

Thereafter, as shown in FIG. 4, the back surface of the sapphire substrate 10 is polished so as to have a thickness of 80 μm or less, and then Ti-Au, Cr-Au, etc. are formed as the back surface metal film 35 and scribed from the back surface. Then, a laser end face and a chip are formed, and a sapphire substrate side is formed by using a fusion metal 37 such as Au-Sn, Pd-Sn, or In for a heat sink 36 made of diamond, copper, or the like.
Mount on 6. Then, the n-side electrode 21 and the p-side electrode 2
A laser element is obtained by bonding a wire 38 to each of the two.

The semiconductor laser obtained as described above has 42
It oscillated continuously at room temperature at a wavelength of 0 nm, the maximum temperature of the continuous operation was 80 ° C., and the operation was continuously performed for 100 hours or more at 50 ° C. and 3 mW. In the above embodiment, the laser oscillation operation can be obtained without forming a layer made of non-doped In _0.15 Ga _0.85 N as the surface protection layer 31, but the maximum oscillation temperature was only 50 ° C. This difference is because the use of the surface protective layer 31 facilitates regrowth and improves the crystal quality of the regrown layer.

In the manufacturing method of the present embodiment, the n-contact layer 12 and the n-cladding layer 1 are formed on the sapphire substrate 10.
3. After forming the MQW active layer 14, the p-cladding layer 15, the current blocking layer 16 and the surface protection layer 31, a part of the surface protection layer 31 and the current blocking layer 16 is removed by RIE or the like to form the p-cladding layer. 15 is exposed. After this, MO
Immediately before forming the buried layer 17 by the CVD method, the substrate temperature is maintained at 1100 ° C. and the surface protective layer 31 is evaporated by exposing to a gas flow atmosphere containing a mixture of ammonia gas, hydrogen gas, and nitrogen gas for 15 minutes, thereby forming a current block. Obtain a clean surface of layer 16. As a result, the occurrence of defects at the interface with the buried layer 17 is suppressed, and the p-
The flattening of the surface of the contact layer 18 is promoted. Therefore, good contact with the p-side electrode 22 formed on the surface of the p-contact layer 18 is formed, and an element having a low operating voltage can be obtained.

In order to further promote such an effect, the surface portion of the current blocking layer has a high Al composition and is difficult to re-evaporate.
The structure can be easily formed by using nGaAlN and forming the surface protective layer from InGaAlN having a low Al composition that easily re-evaporates or containing no Al.

FIG. 5 is a cross-sectional view showing a device structure of a gallium nitride-based compound semiconductor laser according to another embodiment of the present invention, and FIGS. 6A to 6C are cross-sectional views showing manufacturing steps. The present embodiment differs from the embodiment shown in FIG. 1 described above in that the structure and the method of forming the current confinement portion and that a passivation film is newly provided.

In the embodiment shown in FIG. 5, a buffer layer 1 is formed on a sapphire substrate 10 similarly to the embodiment shown in FIG.
1, n-contact layer 12, n-cladding layer 13, MQ
After forming the W active layer 14 and the p-cladding layer 15, as shown in FIG. 6A, a layer made of non-doped In0.15Ga0.85N is formed on the p-cladding layer 15 as the first surface protection layer 51. Grow by 0.2 μm. Subsequently, a non-doped GaN layer is grown as the current blocking layer 16 by 0.6 μm. Further, a layer made of non-doped In _0.15 Ga _0.85 N is grown to a thickness of 0.2 μm as the second surface protection layer 52. At this time, the first and second surface protection layers 51, 52
Is grown at a temperature of 900 ° C. or less in an atmosphere containing nitrogen gas and ammonia gas as main components.

Next, the wafer is taken out from the growth apparatus, and
As shown in (b), a part of the second surface protection layer 52 and the current block layer 16 is etched in a stripe shape having a width of 5 μm to form an opening, and the first surface protection layer 51 is exposed.

Next, the wafer is put into the growth apparatus again, and exposed to a temperature higher than 900 ° C. in an atmosphere containing hydrogen gas as a main component in addition to nitrogen gas and ammonia gas, as shown in FIG. Next, the portion of the first surface protection layer 51 exposed to the opening and the second surface protection layer 52 are evaporated to obtain a clean clad layer surface and a current blocking layer surface.

Next, a Mg-doped GaN p-buried layer 17 and ap ⁺ -GaN p-contact layer 18 are sequentially grown on the current blocking layer 16 and the exposed p-cladding layer 15. Thereafter, the wafer is taken out of the growth apparatus, and the n-contact layer 12 on which the n-side electrode 21 is to be formed is exposed by etching. At this time, the stripe-shaped opening of the current block layer 16 is positioned between the center of the mesa and the n-side electrode 21.
, The series resistance of the current flowing laterally in the n-contact layer 12 can be reduced,
Operation can be reduced.

Next, a passivation film 55 made of SiO ₂ is formed except for an opening for forming an electrode contact, thereby reducing a leak current flowing on a mesa side surface or the like. The opening of the passivation film 55 with respect to the p-side electrode 22 is formed so as to have a wider area including immediately above the stripe-shaped opening of the current constriction.

Next, an n-side electrode 21 made of Ti-Au
A p-side electrode 22 made of Pd-Au is formed. Note that p
The side electrode 22 may be Pt-Au, Ni-Au, or the like. The n-side electrode 21 and the p-side electrode 22 are arranged on the passivation film 55 and are connected to bonding pads arranged on the mesa side surface of the current block layer 16 on the side of the stripe-shaped opening and far from the respective electrode contact portions. . As a result, the damage of the wire bonding can be less likely to reach the light emitting portion.

Further, as in the embodiment shown in FIG. 1, the back surface of the sapphire substrate 10 is polished, the back metal film 35 is formed,
After forming the laser end face and forming a chip, the heat sink 36
Then, the sapphire substrate 10 side is mounted using a fusion metal 37, and wire bonding is performed to each of the n-side electrode 21 and the p-side electrode 22 to obtain a laser element.

The laser device obtained as described above is 420
Continuous oscillation at room temperature with wavelength of nm
An operation of 1000 hours or more at 0 ° C., 50 ° C. and 3 mW was confirmed.

FIG. 7 is a sectional view showing a device structure of a gallium nitride based compound semiconductor laser according to still another embodiment of the present invention.

The embodiment shown in FIG. 7 differs from the embodiment shown in FIG. 1 in that the current block layer is formed of AlN.

That is, in the embodiment shown in FIG. 7, similarly to the embodiment shown in FIG. 1, a buffer layer 11, an n-contact layer 12, and an n-cladding layer 1 are formed on a sapphire substrate 10.
3. After forming the MQW active layer 14 and the p-cladding layer 15, a 30-nm layer of non-doped AlN is grown on the p-cladding layer 15 as the current blocking layer 62. Further, a layer made of non-doped GaN is grown to 0.1 μm as a surface protection layer (not shown). At this time, the surface protective layer is grown in an atmosphere containing nitrogen gas and ammonia gas as main components.

Next, the wafer is taken out of the growth apparatus, a part of the surface protection layer and the current block layer 62 is etched in a stripe shape having a width of 5 μm to form an opening, and the p-clad layer 15 is exposed. Next, the wafer is again put into the growth apparatus, and the temperature is higher than at least the temperature at which the surface protective layer was formed in an atmosphere containing a relatively large amount of hydrogen gas or a small amount of ammonia gas as compared with the atmosphere at the time of forming the surface protective layer. The exposure causes the surface protection layer to evaporate and form a clean current blocking layer surface. Here, since InGaAlN having a high Al composition such as AlN is unlikely to re-evaporate and has a small thickness for preventing current injection, it is not necessary to form an extreme step at the regrowth interface. Regrown crystals are easy to obtain.

Next, on the current block layer 62 and on the exposed p-cladding layer 15, a p-buried layer 17 of Mg-doped GaN and a p-contact layer 18 of p ⁺ -GaN are formed as shown in FIG.
The layers are stacked in the same manner as in the illustrated embodiment.

The wafer thus obtained was made into a laser device in the same manner as in the embodiment shown in FIG. 1, and its characteristics were evaluated. The device continually oscillated at a wavelength of 420 nm at room temperature. Continuous at 50 ° C, 3mW 10
Operation over 00 hours was confirmed.

In the embodiment shown in FIG. 7, the case where no surface protection layer is provided between the p-cladding layer 15 and the current blocking layer 62 has been described. However, for example, the surface protection layer made of p-GaN or the like is described. Needless to say, it may be provided.

FIG. 8 is a sectional view showing a device structure of a gallium nitride based compound semiconductor laser according to still another embodiment of the present invention.

The embodiment shown in FIG. 8 differs from the embodiment shown in FIG. 1 in that a current blocking layer is provided on the substrate side.

That is, in the embodiment shown in FIG. 8, the MOC is formed on the sapphire substrate 10 as in the embodiment shown in FIG.
The buffer layer 11, the n-contact layer 12 are formed by the VD method.
Is formed, a layer made of non-doped or Mg-doped AlN is grown as a current blocking layer 64 on the n-contact layer 12 to a thickness of 30 nm. Further, a layer made of non-doped GaN is used as a surface protection layer (not shown) at a thickness of 0.1 μm.
Let it grow. At this time, the surface protective layer is grown in an atmosphere containing nitrogen gas, hydrogen gas, and ammonia gas as main components.

Next, the wafer is taken out of the growth apparatus, and a part of the surface protection layer and the current block layer 64 is etched into a stripe having a width of 5 μm to form an opening, exposing the n-contact layer 12.

Next, the wafer is put into the growth apparatus again, and in an atmosphere in which the amount of hydrogen gas is relatively large or the amount of ammonia gas is relatively small as compared with the atmosphere in which the surface protective layer is formed, at least the temperature at which the surface protective layer is formed. Exposure to a high temperature evaporates the surface protection layer to obtain a clean current blocking layer surface. The current block layer is less likely to re-evaporate,
It is not necessary to use AlN as long as it is a material that can easily prevent current injection. For example, InGaAlN having a high Al composition may be used.

Next, on the current block layer 64 and the exposed n-contact layer 12, Si-doped Ga _0.8 Al
_{A 0.2N} n-cladding layer 13 is formed with a thickness of 250 nm. Subsequently, an MQW active layer 14 having a multiple quantum well structure having a periodic structure similar to that of the embodiment shown in FIG. 1 is formed. Next, a p-clad layer 15 of Mg-doped Ga _0.8 Al _0.2 N is formed. Further, a buried layer 17 made of Mg-doped p-GaN having a thickness of 0.8 μm is grown, and a 0.2 μm-thick p ⁺ -GaN doped with Mg to a higher concentration than the buried layer 17 is grown thereon. -Contact layer 18
Grow.

The wafer thus obtained was made into a laser device in the same manner as in the embodiment shown in FIG. 1, and its characteristics were evaluated. The device continually oscillated at a wavelength of 420 nm at room temperature. Continuous at 50 ° C, 3mW 10
Operation over 00 hours was confirmed. In addition, due to the light guiding effect in the lateral direction, which is considered to be caused by the bent active layer structure, an astigmatic difference of 10 μm or less, advantageous characteristics for narrowing down to a small spot were obtained.

FIG. 9 is a sectional view showing a device structure of a gallium nitride-based compound semiconductor laser according to still another embodiment of the present invention.

In the embodiment shown in FIG. 9, in addition to the structure of the embodiment shown in FIG. 1, a periodic structure is formed on the side opposite to the substrate having a double hetero junction structure.

That is, in addition to the configuration shown in FIG. 1, the thickness of each layer is set between the current blocking layer 16 and the p-cladding layer 15 and the p-buried layer 17 exposed at the opening of the current blocking layer 16. The periodic structure 66 having a thickness of 10 nm or less and composed of two or more types of gallium nitride-based compound semiconductor layers is formed.

More specifically, both periodic structures 66
GaN / In _0.2 Ga _0.8 N (contact side), a g-doped p-type crystal with a thickness of 2.5 nm (cladding side)
Or a pair of Mg-doped p-type crystals and both having a thickness of 2.5 nm (cladding side) GaN / G
It is composed of 50 pairs of a _0.8 Al _0.2 N (contact side).

With such a structure, in addition to the effect of reducing the crystal defects by the MQW active layer 14 as described in the embodiment shown in FIG. 1, it is possible to reduce the crystal defects by the periodic structure 66. it can. In particular, since the periodic structure portion 66 is located above the current blocking layer 16, defects caused by etching of the current blocking layer 16 can be reduced, which can contribute to a reduction in contact resistance.

In the embodiments described with reference to FIGS. 1 to 9, the periodic structure is MQW in the active layer. However, if the contact layer surface is flattened by forming the periodic structure, and the operating voltage is reduced and the reliability is improved, the periodic structure is formed at least at any part from the electrode contact portion to the active layer. It should just be. Further, the details of the MQW structure can vary depending on the oscillation wavelength, operating current, noise characteristics, and the like, as long as the conditions for promoting flattening of the contact layer surface are satisfied.

Although the current blocking layer is a non-doped high resistance layer, it is not limited to this and various modifications are possible.
For example, n doped with Sn, Se, Te, Ge, S, etc.
-A current blocking layer may be formed and current constriction may be performed by a reverse junction. Further, current constriction may be performed by doping Zn, P, and O to form a deep level, or by doping Mg to form a barrier by a hetero interface.

According to the embodiment described with reference to FIGS. 1 to 9, the periodic structure portion is formed in at least any portion from the electrode contact portion to the active layer.
Crystallinity can be improved without the influence of defects or the like generated during crystal growth. More specifically, defects generated at the time of crystal growth are buried by forming a periodic structure portion, and as a result, crystal quality can be improved. For this reason, it is possible to improve the carrier injection efficiency in the active layer, to suppress the voltage drop at the electrode contact and the like, and to lower the threshold value and improve the reliability.

In the above-described manufacturing method, a surface protective layer is provided in advance on an underlying thin film (for example, a current blocking layer) serving as an underlayer for regrowth, and the surface protective layer is removed after desired etching of the underlying thin film. Evaporation is removed by standing at high temperature in the phase. As a result, a clean surface of the underlying thin film can be obtained, and without exposing it to the atmosphere, etc.
The next layer can be grown continuously. Therefore, the subsequent regrowth is facilitated and the crystal quality of the regrown layer is improved, which contributes to the improvement of the device characteristics of various semiconductor devices using the gallium nitride-based compound semiconductor as well as the semiconductor laser. It becomes possible.

FIG. 10 is a sectional view showing a device structure of a gallium nitride based compound semiconductor laser according to still another embodiment of the present invention.

In the embodiment shown in FIG. 10, a GaN buffer layer 11, a Si-doped GaN n-contact layer 12, a Si-doped GaAl
N n-cladding layer 13, active layer 14 having a multiple quantum well (MQW) structure or the like, Mg-doped GaAlN p-cladding layer 15, Si-doped GaN current blocking layer 16
Are laminated, and the current block layer 16 is etched in a stripe shape.

[0081] On the current blocking layer 16 p- cladding layer 15 exposed by etching and the current blocking layer 16, Mg-doped GaN of p- lower current injection layer 17, p of a high concentration of Mg doped p ⁺ -GaN An upper current injection layer (p-contact layer) 18 is laminated; And p-
The n-contact layer 1 which is partially etched from the contact layer 18 to the middle of the n-contact layer 12 and is exposed
2, an n-side electrode 21 is formed on the surface, and a p-side electrode 22 is formed on the surface of the p-contact layer 18. Next, a method of manufacturing the gallium nitride based compound semiconductor laser shown in FIG. 10 and details of its structure will be described.

First, GaN, AlN, and the like are formed on the sapphire substrate 10 by metal organic chemical vapor deposition (MOCVD) or the like.
The buffer layer 11 made of GaAlN or the like has a thickness of 10 to 200 n.
m and a thickness of n of Si-doped GaN
Forming the contact layer 12 to a thickness of 4 μm; Subsequently, an n-cladding layer 1 of Si-doped Ga _0.85 A1 _0.15 N
3 is formed with a thickness of 300 nm. Although the growth method is not described below, it is assumed that the MOCVD method is used in all cases.

Next, a non-doped GaN having a thickness of 1
00 nm light guide layer, 2 nm thick non-doped In
_0.2 Ga _0.8 N and 4 nm thick non-doped In _0.05
Ga 2 types of multiple quantum well (MQW) structure composed of an InGaAlN layer by repeating 10 cycles of _{0. 95} N, made of Mg-doped Al _0.2 Ga _0.8 N, a thickness of 40 nm p-
Cap layer, and Mg-doped GaN, thickness 1
An active layer 14 is formed by laminating a 00 nm p-light guide layer.

Next, the p of Mg-doped Ga _0.85 Al _0.15 N
Forming the cladding layer 15 to a thickness of 300 nm, and subsequently growing a layer made of Si-doped GaN as the current blocking layer 16 to 1.5 μm.

Next, the wafer is taken out of the growth apparatus, and a part of the current block layer 16 is etched into a stripe having a width of 3 μm by reactive ion etching (RIE) to form an opening, and the p-cladding layer 15 is formed. Expose.

Next, the wafer is again put into the growth apparatus, and a p-lower current injection layer 17 made of Mg-doped p-GaN and having a thickness of 800 nm is formed on the current block layer 16 and the exposed p-cladding layer 15. High concentration Mg doped p ⁺
A p-upper current injection layer (p-contact layer) 18 made of GaN and having a thickness of 200 nm is laminated.

Next, the wafer is taken out of the growth apparatus, and p
Partially etching by RIE from the contact layer 18 to the middle of the n-contact layer 12 to expose the n-contact layer where the n-side electrode is to be formed;

Next, on the n-contact layer 12, Al-T
An n-side electrode 21 made of i-Au is formed. Also, p-
A p-side electrode 22 made of Pt-Ti-Pt-Au is formed on the contact layer 18 so as to have a wider area including immediately above the stripe-shaped opening of the current block layer. Thus, the structure shown in FIG. 10 is obtained.

The laser device obtained as described above is 420
Continuous oscillation at room temperature at a wavelength of nm
It was confirmed that operation was performed at 00 ° C., 50 ° C., and 3 mW for continuous 1000 hours or more.

As a component requirement for obtaining such element characteristics, the thickness of the current blocking layer 16 is set to TA, p−
The thickness of the cladding layer 15 (the current blocking layer 16 and the active layer 1
4), TB, p-lower current injection layer 1
7 and p−the sum of the thicknesses of the upper current injection layers 18, that is, the thickness of the current injection layer (p between the current blocking layer 16 and the electrode 22).
−thickness of the layer) as TC, the relationship between the thicknesses is set so as to satisfy TB <TA (1) TC <TA (2) TB <TC (3) is there.

In the embodiment shown in FIG. 10, the thickness of the current blocking layer 16 is set to be larger than the thickness of the p-cladding layer 15, that is, the distance between the current blocking layer and the active layer 14. The thickness of the current injection layer is made larger than the thickness of the current injection layer, and the thickness of the current injection layer is made larger than the distance between the current block layer 16 and the active layer. However, a good current confinement effect was obtained even under such a condition that at least one of the thicknesses was satisfied. In addition, by meeting some or all of these requirements,
The effect of giving the element characteristics became larger.

Further, the above-mentioned effect can be further suppressed by setting 2TB <TA (4) because the p-type impurity contamination due to the memory effect described later can be further suppressed. . However, the current blocking layer 1
When the thickness of No. 6 is larger than 10 times the distance between the current blocking layer 16 and the active layer 14, it is difficult to form the opening of the current blocking layer 16 with good controllability, and the yield is reduced.

The above effect can be further suppressed by mixing 1.2 p <TA (5), whereby p-type impurity contamination due to diffusion can be further suppressed, so that a better current confinement effect can be obtained. However, if the thickness of the current blocking layer 16 is larger than twice the thickness of the current injection layer, sufficient crystallinity cannot be obtained at the portion where the current injection layer is formed in the opening of the current blocking layer 16. The electrode contact formed on the current injection layer was insufficient, causing an increase in operating voltage.

Further, it is preferable that 1.7 TB <TC <5 TB (6). Here, the thickness of the current injection layer is p
-If the thickness of the cladding layer 15 is larger than the above range, the series resistance increases and the operating voltage increases. Conversely, if the thickness is smaller than the above range, light confinement becomes insufficient.

In the embodiment shown in FIG. 10, an active layer having MQW has been described. However, a single quantum well (SQW), a thick layer having no quantum effect, or a layer having no quantum effect is used. A structure in which a plurality of layers are separated by a layer having a large band gap may be employed.

Further, a p-type layer is provided between the active layer and the current blocking layer.
When a p-layer other than the cladding layer is inserted, the thickness of the p-layer is set as a part of the thickness TB of the p-cladding layer 15 so as to satisfy the above conditions.

FIG. 11 is a sectional view showing a device structure of a gallium nitride based compound semiconductor laser according to still another embodiment of the present invention. FIG. 12 shows a profile of impurity doping around the current confinement portion in the embodiment shown in FIG.

In the embodiment shown in FIG. 11, a buffer layer 11, an n-contact layer 12, an n-cladding layer 13, an active layer 14, a p-cladding layer 15, and a current block of Si-doped GaN are formed on a sapphire substrate 10. A layer 16 is formed, and the current block layer 16 is etched in a stripe shape.

On the p-cladding layer 15 and the current block layer 16 exposed by the etching of the current block layer 16, the p-lower current injection layer 17 and the p-upper current injection layer (p
-Contact layer) 18 is laminated. The n-side electrode 21 is formed on the exposed surface of the n-contact layer 12 by being partially etched from the p-contact layer 18 to the middle of the n-contact layer 12.
The p-side electrode 22 is formed on the surface of the substrate 8.

Next, a method of manufacturing the gallium nitride based compound semiconductor laser shown in FIG.

On the active layer 14, a p-cladding layer 15 of p-Ga _0.85 Al _0.15 N doped with 3 × 10 ¹⁹ cm ⁻³ of Mg.
Is formed to a thickness of 300 nm, and then a current blocking layer 16 of GaN doped with 3 × 10 ¹⁸ cm ⁻³ of Si is grown as the current blocking layer 16 by 1.5 μm. Next, the wafer is removed from the growth apparatus, and the current block layer 1 is removed.
6 is etched by reactive ion etching (RIE) into a stripe having a width of 3 μm to form an opening.
Exposing the cladding 15; Next, the wafer is again put into the growth apparatus, and p-GaN of p-GaN doped with 3 × 10 ¹⁹ cm ^{−3 of} Mg and having a thickness of 800 nm is formed on the current blocking layer 16 and the exposed p-cladding layer 15. Lower current injection layer 17, p ⁺ -G doped with 8 × 10 ¹⁹ cm ^{−3 of} Mg
A p-upper current injection layer (p-contact layer) 18 made of aN and having a thickness of 200 nm is laminated. Next, an electrode forming process similar to that of the embodiment shown in FIG.
1 is obtained.

In the current block layer 16, as shown in FIG. 11, regions 16a and n indicating p-type or high-resistance i-type are formed.
A region 16b indicating a pattern and a region 16c indicating a p-type or a high-resistance i-type are formed. The region 16a showing the p-type or high-resistance i-type is formed by the current block layer 16 and its underlying p-type region.
-Formed close to the interface of the cladding layer 15; Also,
The region 16c showing p-type or high-resistance i-type is formed close to the interface between the current blocking layer 16 and the p-lower current injection layer 17. This structure can be formed by mixing Mg, which is a p-type impurity, into the current block layer so as to have a desired profile by utilizing an effect described later and a diffusion effect. Note that typical thicknesses of the regions 16a and 16c are approximately 600 nm and 200 nm, respectively.

Defects such as minute holes are likely to occur at the interface between the current blocking layer 16 and the p-layer below it or at the interface between the current blocking layer 16 and the p-current injection layer. When these interfaces and the pn junction surface are positioned substantially equal, it causes a reactive current due to recombination caused by a defect existing in the pn junction surface, and inhibits current constriction. On the other hand, by positively shifting the interface between the pn junction surface and the crystal layer in the current block layer as in the embodiment shown in FIG. 11, invalidity caused by recombination caused by defects existing in the pn junction surface is obtained. The current is reduced. As a result, it is possible to lower the threshold voltage, lower the voltage, and improve the reliability. In particular, as shown in the present embodiment, Al
When a current blocking layer is formed in contact with a crystal layer containing, it is easy for defects to be generated in the current blocking layer near the interface,
The effect of the present invention appears remarkably.

Actually, the laser device obtained as described above continually oscillated at a wavelength of 420 nm at room temperature, and it was confirmed that the continuous operation was performed at the maximum temperature of 120 ° C., 50 ° C. and 3 mW for a continuous 3,000 hours or more. .

The non-n-type region shown in the embodiment shown in FIG. 11 is provided at both the interface between the current block layer and the layer below the current block layer where defects easily occur and the interface between the current block layer and the p-current injection layer. I have. However, it is effective even if it is formed only on one of the interfaces. Further, the non-n-type region is formed by Mg used when forming a layer other than the current block layer.
Is formed by mixing a p-type impurity such as But,
It may be formed by intentionally doping a p-type impurity during formation of the current blocking layer.

FIG. 13 is a sectional view showing a device structure of a gallium nitride-based compound semiconductor laser according to still another embodiment of the present invention.

In the embodiment shown in FIG. 13, a buffer layer 11, an n-contact layer 12, an n-cladding layer 13, an active layer 14, a first p-cladding layer 15, and a current blocking layer 16 are formed on a sapphire substrate 10. The current blocking layer 16 is laminated and etched in a stripe shape.

First p-cladding layer 15 and current blocking layer 16 exposed by etching of current blocking layer 16
Above, a p-lower current injection layer (second p-cladding layer) 1
7. A p-upper current injection layer (p-contact layer) 18 is laminated. The n-side electrode 21 is formed on the exposed surface of the n-contact layer 12 by being partially etched from the p-contact layer 18 to the middle of the n-contact layer 12, and is formed on the surface of the p-contact layer 18. p-side electrode 22
Is formed.

Next, a method of manufacturing the gallium nitride based compound semiconductor laser shown in FIG.

[0110] The active layer 14, an undoped GaN, the light guide layer having a thickness of 100 nm, 2 kinds of InGaAlN of undoped In _0.2 Ga _0.8 N, and a thickness of 4nm undoped In _{0. 05} Ga _0.95 N having a thickness of 2nm 10 layers
Multiple quantum well (MQW) structure composed of periodic repetitions, made of Mg-doped Al _0.2 Ga _0.8 N and having a thickness of 40
A 100 nm-thick p-cap layer and a 100 nm-thick p-light guide layer made of Mg-doped GaN are stacked and grown. Mg is formed on the active layer 14 doped Ga _0.85 Al _{0. 15} N
Is formed with a thickness of 100 nm, and then a current blocking layer of Si-doped Ga _0.8 Al _0.2 N is grown to a thickness of 300 nm. Current blocking layer 16
After etching the striped μm width, the first 2p- cladding layer 17 of Mg-doped Ga _0.85 Al _{0. 15} N 300
nm. Next, p ⁺ − doped with Mg at a high concentration
A 200 nm-thick p-upper current injection layer (p-contact layer) 18 made of GaN is laminated. Next, an electrode forming process similar to that of the embodiment shown in FIG.
3 is obtained.

In the structure shown in the embodiment shown in FIG.
The second p-cladding layer 17 corresponding to at least a portion of the current injection layer close to the active layer is formed by the light emitting wavelength 4 of the active layer 14.
It has a band gap larger than the band gap corresponding to 20 nm. Further, the refractive index of the second p-cladding layer 17 is larger than that of the current blocking layer 16.

As a result, a high light guiding mechanism can be formed at the stripe-shaped opening where the current is injected with an effective refractive index in the direction parallel to the junction, the fundamental transverse mode is stabilized, and the light absorption loss and diffraction The increase in the threshold current due to the loss was suppressed, and the wavefront of the guided light was flattened, thereby achieving a small astigmatic difference indispensable as a laser for an optical disk.

Actually, the laser device obtained as described above continually oscillates at a wavelength of 420 nm at room temperature, the maximum temperature of continuous operation is 120 ° C., and the continuous operation is 1000 ° C. under the conditions of 50 ° C. and 5 mW.
Operation over time was confirmed. The astigmatic difference is 3
A small value of less than μm was obtained.

In the embodiment shown in FIG. 13, the first
By forming the p-cladding layer 15 and the second p-cladding layer 17 with the same material, the layers have substantially the same refractive index. However, at least a portion of the current injection layer, which is the gist of the present invention, near the active layer has a band gap larger than the band gap corresponding to the emission wavelength of the active layer, and has a refractive index larger than that of the current blocking layer. The same effect can be obtained if it is satisfied.

FIG. 14 is a sectional view showing a device structure of a gallium nitride-based compound semiconductor laser according to still another embodiment of the present invention.

In the embodiment shown in FIG. 14, a buffer layer 11, an n-contact layer 12, an n-cladding layer 13, an active layer 14, a first p-cladding layer 15, and a current blocking layer 16 are formed on a sapphire substrate 10. The current blocking layer 16 is laminated and etched in a stripe shape.

First p-cladding layer 15 and current blocking layer 16 exposed by etching of current blocking layer 16
Above, a p-lower current injection layer (second p-cladding layer) 1
7. A p-upper current injection layer (p-contact layer) 18 is laminated. The n-side electrode 21 is formed on the exposed surface of the n-contact layer 12 by being partially etched from the p-contact layer 18 to the middle of the n-contact layer 12, and is formed on the surface of the p-contact layer 18. p-side electrode 22
Is formed.

Next, a method of manufacturing the gallium nitride-based compound semiconductor laser shown in FIG.

[0119] The active layer 14, an undoped GaN, the light guide layer having a thickness of 100 nm, 2 kinds of InGaAlN of undoped In _0.2 Ga _0.8 N, and a thickness of 4nm undoped In _{0. 05} Ga _0.95 N having a thickness of 2nm 10 layers
Multiple quantum well (MQW) structure composed of periodic repetitions, made of Mg-doped Al _0.2 Ga _0.8 N and having a thickness of 40
A 100 nm-thick p-cap layer and a 100 nm-thick p-light guide layer made of Mg-doped GaN are stacked and grown. Mg is formed on the active layer 14 doped Ga _0.85 Al _{0. 15} N
The first p-cladding layer 15 is formed with a thickness of 100 nm, and then a current blocking layer of Si-doped Ga _0.85 Al0.15N is grown to 300 nm. Current blocking layer 16
After etching the striped μm width, the first 2p- cladding layer 17 of Mg-doped Ga _0.9 Al _{0. 1} N 300
nm. Next, p ⁺ − doped with Mg at a high concentration
A 200 nm-thick p-upper current injection layer (p-contact layer) 18 made of GaN is laminated. Next, an electrode forming process similar to that of the embodiment shown in FIG.
4 is obtained.

In the structure shown in the embodiment shown in FIG.
The current blocking layer 16 has a band gap larger than the band gap corresponding to the emission wavelength of the active layer 14. Further, the refractive index of the current blocking layer 16 is the second p-type, which corresponds to at least a portion of the current injection layer close to the active layer.
It is larger than the refractive index of the cladding layer 17.

As a result, a light guide mechanism of low light can be formed at the stripe-shaped opening into which the effective refractive index in the direction parallel to the junction is injected with current, thereby stabilizing the fundamental transverse mode and reducing the light absorption loss. In addition to suppressing the increase in the threshold current, the wavefront of the guided light was flattened, and a small astigmatic difference indispensable as a laser for an optical disk could be realized.

Actually, the laser device obtained as described above continuously oscillates at a wavelength of 420 nm at room temperature, the maximum temperature of the continuous operation is 100 ° C., and the maximum temperature is 1000 ° C. at 50 ° C. and 5 mW.
Operation over time was confirmed. The astigmatic difference is 3
A small value of less than μm was obtained.

In the embodiment shown in FIG. 14, the first
By forming the p-cladding layer 15 and the current blocking layer 16 from the same material having different conductivity types, the layers have substantially the same refractive index. However, the current blocking layer, which is the gist of the present invention, has a band gap larger than the band gap corresponding to the emission wavelength of the active layer, and has a refractive index larger than at least a portion of the current injection layer close to the active layer. Is satisfied, the same effect can be obtained.

FIG. 15 is a sectional view showing an element structure of a gallium nitride-based compound semiconductor laser according to still another embodiment of the present invention.

In the embodiment shown in FIG. 15, a buffer layer 11, an n-contact layer 12, an n-cladding layer 13, an active layer 14, a first p-cladding layer 15, and a current blocking layer 16 are formed on a sapphire substrate 10. The current blocking layer 16 is laminated and etched in a stripe shape.

First p-cladding layer 15 and current blocking layer 16 exposed by etching of current blocking layer 16
Above, a p-lower current injection layer (second p-cladding layer) 1
7. A p-upper current injection layer (p-contact layer) 18 is laminated. The n-side electrode 21 is formed on the exposed surface of the n-contact layer 12 by being partially etched from the p-contact layer 18 to the middle of the n-contact layer 12, and is formed on the surface of the p-contact layer 18. p-side electrode 22
Is formed.

Next, details of the method of manufacturing the gallium nitride based compound semiconductor laser of the embodiment shown in FIG.

The active layer 14 is made of non-doped GaN and has a thickness of 100 nm, a non-doped In _0.2 Ga _0.8 N layer having a thickness of 2 nm, and a non-doped In layer having a thickness of 4 nm.
_A multiple quantum well (MQW) structure composed of two repeating InGaAlN layers of _0.05 Ga _0.95 N for 10 periods;
It is formed by laminating a p-cap layer made of g-doped Al _0.2 Ga _0.8 N and having a thickness of 40 nm and a p-light guide layer made of Mg-doped GaN and having a thickness of 100 nm.
The on the active layer 14 to form a first 1p- cladding layer 15 of Mg-doped p-Ga _0.85 Al _0.15 N with a thickness of 100 nm,
Next, a current blocking layer of Si-doped In _0.25 Ga _0.75 N is grown to a thickness of 300 nm. The current block layer 16 is 3 μm
After etching into stripes of width, Mg-doped Ga
_0.85 Al _0.15 N second p-cladding layer 17 is 300 nm
Form. Next, p ⁺ -Ga doped with Mg at a high concentration
P-upper current injection layer (p
-Contact layer) 18 is laminated. Next, through the same electrode forming process as the embodiment shown in FIG. 10, the structure shown in FIG. 15 is obtained.

In the structure shown in the embodiment shown in FIG.
The band gap of the second p-clad layer 17 corresponding to at least a portion of the current injection layer close to the active layer is larger than the band gap corresponding to the emission wavelength of the active layer. Further, the band gap of the current blocking layer 16 is smaller than the band gap corresponding to the emission wavelength of the active layer.

As a result, a high light guiding mechanism can be formed at the stripe-shaped opening into which the effective refractive index in the direction parallel to the junction is injected with current, and the absorption loss for the higher-order transverse mode is increased. Stabilizing the fundamental transverse mode, suppressing the increase in threshold current due to light diffraction loss, flattening the wavefront of guided light, and reducing the small astigmatic difference indispensable for lasers for optical discs. Could be realized.

Actually, the laser device obtained as described above continually oscillates at a wavelength of 420 nm at room temperature, and has a maximum continuous operation temperature of 100 ° C. and a continuous temperature of 1000 ° C. under the conditions of 50 ° C. and 7 mW.
Operation over time was confirmed. The astigmatic difference is 7
A small value of less than μm was obtained.

In the embodiment shown in FIG. 15, the first
By forming the p-cladding layer 15 and the second p-cladding layer 17 with the same material, the layers have substantially the same refractive index. However, the band gap of at least a portion of the current injection layer, which is the essence of the present invention, close to the active layer is larger than the band gap for the emission wavelength of the active layer, and the band gap of the current blocking layer corresponds to the emission wavelength of the active layer. The same effect can be obtained if the condition of smaller than the band gap is satisfied.

FIG. 16 is a sectional view showing a device structure of a gallium nitride based compound semiconductor laser according to still another embodiment of the present invention.

In the embodiment shown in FIG. 16, a buffer layer 11 and an n-contact layer 1 are formed on a sapphire substrate 10.
2. An n-cladding layer 13, an active layer 14, a p-cladding layer 15, and a current blocking layer 16 are laminated, and the current blocking layer 16 and the p-cladding layer 15 are etched in a stripe shape, and the cross-sectional shape thereof is V-shaped. It is in shape.

Current Blocking Layer 16 and p-Clad Layer 1
5 of the p-cladding layer 15 exposed by the etching of FIG.
A p-lower current injection layer 17 and a p-upper current injection layer (p-contact layer) 18 are formed on the groove and the current block layer 16.
Are laminated. Then, from the p-contact layer 18 to the n-
Partially etched partway through the contact layer 12,
The n-side electrode 21 is provided on the exposed surface of the n-contact layer 12.
Is formed, and a p-side electrode 22 is formed on the surface of the p-contact layer 18.

Next, a method of manufacturing the gallium nitride based compound semiconductor laser of the embodiment shown in FIG.

The active layer is made of non-doped GaN and has a thickness of 100 nm.
_0.2 Ga _0.8 N and 4 nm thick non-doped In _0.05
A multiple quantum well (MQW) structure constituted by repeating two kinds of InGaAlN layers of Ga _0.95 N for 10 periods, which is composed of Mg-doped Al _0.2 Ga _0.8 N and has a thickness of 40 nm
Cap layer, and Mg-doped GaN, thickness 1
It is formed by laminating a p-light guide layer having a thickness of 00 nm. On the active layer 14, a p-clad layer 15 of Mg-doped Ga _0.85 Al _0.15 N is formed with a thickness of 300 nm, and then a current blocking layer of GaN doped with Si is formed to a thickness of 1.5 μm. The V-shaped groove reaching the p-cladding layer 15 is formed by etching the current block layer 16 into a stripe having a width of 2 μm, and then a p-lower current injection layer 17 of Mg-doped GaN is formed to a thickness of 800 nm. Next, it is made of p ⁺ -GaN doped with Mg at a high concentration, and has a thickness of 200
A nm-p-upper current injection layer (p-contact layer) 18 is laminated. Next, through the same electrode forming process as the embodiment shown in FIG. 10, the structure shown in FIG. 16 is obtained.

In the structure shown in the embodiment shown in FIG.
The p-lower current injection layer 17 is formed so as to be in contact with the groove formed in the p-cladding layer 15 sandwiched between the current injection layer and the active layer 14 at the stripe-shaped opening.
Another feature is that the shape of the groove is V-shaped.

As a result, the current can be concentrated at the center of the stripe, and an invalid current due to current spreading can be suppressed. Further, it is considered that making the resistivity of the p-lower current injection layer 17 lower than the resistivity of the p-cladding layer 15 results in a more significant reactive current confinement effect. In this case, at the same time, since the refractive index of the material to be embedded in the V-shaped groove is higher than the refractive index of the p-cladding layer, the effective refractive index in the direction parallel to the junction is V-shaped in the stripe-shaped opening where current is injected. A high light guiding mechanism can be formed in the part, stabilizing the fundamental transverse mode, suppressing the increase in threshold current due to light absorption loss and diffraction loss,
By flattening the wavefront of the guided light, a small astigmatic difference indispensable as a laser for an optical disk could be realized.

Actually, the laser device obtained as described above continually oscillates at a wavelength of 420 nm at room temperature, and has a maximum continuous operation temperature of 110 ° C. and a continuous temperature of 50 ° C. and 3 mW.
Operation over time was confirmed. The astigmatic difference is 7
A small value of less than μm was obtained.

In the embodiment shown in FIG. 16, a layer having a higher refractive index than the p-clad layer 15 is used as the p-lower current injection layer 17. However, if the resistivity is lower than that of the p-cladding layer 15, not only a layer having a high refractive index but also a material having a substantially equal refractive index or a material having a low refractive index may be used.

FIG. 17 is a sectional view showing a device structure of a gallium nitride-based compound semiconductor laser according to still another embodiment of the present invention.

In the embodiment shown in FIG. 17, a buffer layer 11, an n-contact layer 12, an n-cladding layer 13, an active layer 14, a p-cladding layer 15, and a current block layer 16 are laminated on a sapphire substrate 10. The current blocking layer 16 and the p-cladding layer 15 are formed and etched in a stripe shape, and the cross-sectional shape is flat at the groove bottom.

Current Blocking Layer 16 and p-Clad Layer 1
A p-lower current injection layer 17 and a p-upper current injection layer (p-contact layer) 18 are stacked on the groove of the p-cladding layer 15 and the current block layer 16 exposed by the etching of Step 5. The n-side electrode 21 is formed on the exposed surface of the n-contact layer 12 by being partially etched from the p-contact layer 18 to the middle of the n-contact layer 12, and is formed on the surface of the p-contact layer 18. p-side electrode 2
2 are formed.

Next, a method of manufacturing the gallium nitride-based compound semiconductor laser shown in FIG.

The active layer is made of non-doped GaN and has a thickness of 100 nm.
_0.2 Ga _0.8 N and 4 nm thick non-doped In _0.05
A multiple quantum well (MQW) structure constituted by repeating two kinds of InGaAlN layers of Ga _0.95 N for 10 periods, which is composed of Mg-doped Al _0.2 Ga _0.8 N and has a thickness of 40 nm
Cap layer, and Mg-doped GaN, thickness 1
It is formed by laminating a p-light guide layer having a thickness of 00 nm. On the active layer 14, a p-cladding layer 15 of Mg-doped Ga _0.85 Al _0.15 N is formed to a thickness of 300 nm, and then a current blocking layer of Si-doped GaN is formed to a thickness of 1.5 μm. After the current block layer 16 is etched into a stripe shape having a width of 3 μm, the groove reaches the p-cladding layer 15 and has a cross-sectional shape that is flat at the groove bottom.
800 n of p-lower current injection layer 17 of Mg-doped GaN
m. Next, p ⁺ -G doped with Mg at a high concentration
A p-upper current injection layer (p-contact layer) 18 made of aN and having a thickness of 200 nm is laminated. Next, an electrode forming process similar to that of the embodiment shown in FIG.
The structure shown in FIG. 7 is obtained.

In the structure shown in the embodiment shown in FIG.
The p-lower current injection layer 17 is formed so as to be in contact with the groove formed in the p-cladding layer 15 sandwiched between the current injection layer and the active layer 14 at the stripe-shaped opening.
Another feature is that the shape of the groove is such that its cross-sectional shape is flat at the groove bottom.

As a result, the width of the current injection and the width of the light guiding mechanism can be made substantially the same. This is effective for producing a laser having a small astigmatic difference. Since the refractive index of the material filling the groove is higher than the refractive index of the p-clad layer,
A high light guiding mechanism can be formed at the stripe-shaped opening where the effective refractive index in the direction parallel to the junction is injected, stabilizing the fundamental transverse mode and reducing the threshold current due to light absorption loss and diffraction loss. While suppressing the increase, the wavefront of the guided light was flattened, and a small astigmatic difference indispensable as a laser for an optical disk could be realized.

Actually, the laser device obtained as described above continually oscillates at a wavelength of 420 nm at room temperature and has a maximum continuous operation temperature of 110 ° C. and a continuous temperature of 1000 ° C. under the conditions of 50 ° C. and 5 mW.
Operation over time was confirmed. The astigmatic difference is 5
A small value of less than μm was obtained.

In the embodiment shown in FIG. 17, GaN having a higher refractive index than the p-cladding layer 15 is used as the p-lower current injection layer 17, but as shown in FIG. Second p with equivalent or lower refractive index
-The cladding layer 17a or the like may be used.

FIG. 19 is a sectional view showing a device structure of a gallium nitride based compound semiconductor laser according to still another embodiment of the present invention. The embodiment shown in FIG. 19 is different from the embodiment shown in FIG. 17 only in that the groove formed in the p-cladding layer has two stages, and the width of the groove is smaller than the width of the stripe-shaped opening. This embodiment is different from the above embodiment.

With this configuration, the width of the current injection can be made smaller than the width of the optical waveguide mechanism.
This promotes absorption in the non-injection portions on both sides of the current injection portion of the active layer, and is effective for forming a supersaturated absorber to produce a low-noise laser causing self-pulsation.

Actually, the laser device obtained as described above continually oscillates at a wavelength of 420 nm at room temperature, the maximum temperature of continuous operation is 90 ° C., and operation for 1000 hours or more at 50 ° C. and 5 mW can be confirmed. Was. The astigmatic difference is 7μ
m and smaller values were obtained. In addition, low noise characteristics causing self-pulsation were obtained.

In the embodiment shown in FIG. 19, a layer having a higher refractive index than the p-cladding layer is used as the p-lower current injection layer. However, if the resistivity is lower than that of the p-cladding layer 15, not only a layer having a high refractive index but also a material having a substantially equal refractive index or a material having a low refractive index may be used.

According to the embodiment shown in FIGS. 10 to 19, the following effects can be obtained.

In a conventional semiconductor laser device having a stripe opening in a current block layer, a crystal of the current block layer is formed by doping an n-type impurity such as Si and not intentionally doping a p-type impurity such as Mg. During the growth, a phenomenon is observed in which a p-type impurity material such as Mg is taken into the current block layer crystal. This is because a p-type impurity material such as Mg to be doped when forming a cladding layer or the like located between the current blocking layer and the active layer is formed on the inner wall of the reaction furnace of the crystal growth apparatus,
This is considered to be due to the fact that the p-type impurity material such as Mg is desorbed from the inner wall of the reactor, the piping and the like of the crystal growth apparatus during the crystal growth of the current block layer (memory effect).

Further, impurities such as Mg doped in a cladding layer or the like located between the current blocking layer and the active layer, or in a current injection layer formed on the current blocking layer may cause a crystal growth or an element structure forming process. During the heat treatment during the
Diffusion into the current blocking layer. Due to these effects, the current blocking layer must have low crystallinity with unintended impurities. In particular, the current blocking layer, which originally provides good current confinement by being made n-type, is no longer n-type due to the incorporation of p-type impurities, and the current constriction is impaired, generating an invalid current. Also, when trying to maintain n-type by doping a larger amount of n-type impurities than the mixed p-type impurities, a large amount of n-type doping impairs crystallinity and causes a reactive current.

On the other hand, according to the present invention, as described in the embodiment shown in FIG. 10, the thickness of the current blocking layer is made smaller than the thickness of the p-layer between the current blocking layer and the active layer. The above problem can be solved by increasing the thickness. That is, with this structure, even if a p-type impurity that is not intentionally doped due to the above-described influence is mixed into the current block layer, an n-type region can be left in at least a part, so that the current confinement effect is improved. . This is in consideration of the fact that the amount of the impurity material adhering / desorbing to the reaction furnace or the piping due to the memory effect increases depending on the time for forming the layer, that is, the thickness of the layer. P between the current blocking layer and the active layer
Increasing the thickness of the current blocking layer according to the thickness of the layer can leave an n-type region at least partially; As a result, the reactive current is reduced, and the threshold value, the voltage, and the reliability can be improved.

Further, according to the present invention, by making the thickness of the current blocking layer larger than twice the distance between the current blocking layer and the active layer, the p-type impurity contamination due to the memory effect can be further suppressed. it can. Therefore, a good current confinement effect can be obtained without excessively increasing the n-type doping amount, and it is possible to further lower the threshold voltage, lower the voltage, and improve the reliability. However, if the thickness of the current block layer is larger than 10 times the distance between the current block layer and the active layer, it becomes difficult to form the opening of the current block layer with good controllability, and the yield may decrease. Therefore, there is a substantial upper limit of the thickness.

Further, according to the present invention, by making the thickness of the current blocking layer larger than the thickness of the current injection layer,
Even if a p-type impurity that is not intentionally doped is mixed into the current blocking layer by diffusion during the formation of the current injection layer, the n-type region can be left in at least a part, so that the current confinement effect is improved. This is because the amount of the diffused p-type impurity increases depending on the time for forming the current injection layer, that is, the thickness. Therefore, by increasing the thickness of the current block layer accordingly, the n-type region is at least partially formed. It depends on what you can leave. As a result, the reactive current is reduced, and the threshold value, the voltage, and the reliability can be improved.

Further, according to the present invention, by making the thickness of the current blocking layer larger than 1.2 times the thickness of the current injection layer, the p-type impurity contamination due to diffusion can be further suppressed. . Therefore, a good current confinement effect can be obtained without excessively increasing the n-type doping amount, and it is possible to further lower the threshold voltage, lower the voltage, and improve the reliability. However, when the thickness of the current blocking layer is larger than twice the thickness of the current injection layer, sufficient crystallinity cannot be obtained at the portion where the current injection layer is formed in the opening of the current blocking layer, and the current injection There is a substantial upper limit on the thickness since the electrode contacts formed on top of the layer become insufficient and cause an increase in operating voltage.

Further, according to the present invention, the thickness of the current injection layer is made larger than the distance between the current block layer and the active layer, so that the thickness between the current block layer and the active layer is increased by the heat treatment in the device fabrication process. The strain of the located clad layer is alleviated, and the generation of cracks (cracks) in the crystal can be prevented. Therefore, a good current confinement effect can be obtained, and it is possible to lower the threshold voltage, lower the voltage, and improve the reliability. However, it is desirable that the thickness of the current injection layer is between 1.7 and 5 times the distance between the current blocking layer and the active layer. Here, when the thickness of the current injection layer is larger than the above range with respect to the distance between the current blocking layer and the active layer (the thickness of the p-clad layer),
When the series resistance increases and the operating voltage increases, and conversely, becomes smaller than the above range, light confinement becomes insufficient.

On the other hand, in a conventional gallium nitride based semiconductor laser device having a stripe opening in a current block layer, n
-Defects such as minute holes are likely to occur at the interface between the current blocking layer and the p-layer below it or at the interface between the current blocking layer and the p-current injection layer. Since the interface between these layers and the pn junction surface are positioned substantially equal, it causes a reactive current due to the coupling generated by a defect existing in the pn junction surface, and inhibits current constriction.

On the other hand, according to the present invention, at least a non-n-type region is formed in the current block layer doped with an n-type impurity such as Si, and the interface between the pn junction surface and the crystal layer is positively shifted. . As a result, reactive current due to recombination generated by defects existing at the pn junction interface can be reduced, and lower threshold voltage, lower voltage, and improved reliability can be achieved.

The non-n-type region is desirably provided at the interface between the current block layer and the lower layer where defects easily occur, the interface between the current block layer and the p-type current injection layer, or both. In addition, the non-n-type region is
It is desirable that a p-type impurity such as Mg is added to form a low-concentration p-type or a high-resistance i-type. Further, since the carrier concentration profile changes continuously, the electric field is not locally concentrated, and the reactive current can be further suppressed.

On the other hand, in the conventional gallium nitride based semiconductor laser device having a stripe opening in the current block layer, the effective refractive index in the direction parallel to the junction is constant, and the light guide mechanism and the stabilization of the fundamental transverse mode are stabilized. No mechanism has been formed. As a result, higher-order transverse modes occur, threshold current increases due to absorption loss and diffraction loss, and large astigmatic difference occurs due to the curvature of the guided optical wavefront. It was difficult to realize.

On the other hand, according to the present invention, at least a portion of the current injection layer close to the active layer has a band gap larger than the band gap corresponding to the emission wavelength of the active layer, and has a larger refractive index than the current blocking layer. It can be. As a result, a high light guiding mechanism can be formed at the stripe-shaped opening where the effective refractive index in the direction parallel to the junction is injected with current, stabilizing the fundamental transverse mode, and reducing the light absorption loss and diffraction loss. In addition to suppressing the increase in the threshold current, the wavefront of the guided light is flattened, and a small astigmatic difference indispensable as a laser for an optical disk can be realized.

In the above structure, the refractive index of the cladding layer between the current injection layer and the active layer, the refractive index of the current blocking layer, or the refractive index of at least a portion of the current injection layer close to the active layer Can be made substantially equal. This eliminates the need to control subtle differences in the refractive index, facilitates manufacture, and provides a semiconductor laser with high reproducibility and high yield.

According to the present invention, the current blocking layer has a band gap larger than the band gap corresponding to the emission wavelength of the active layer, and has a refractive index larger than at least a portion of the current injection layer close to the active layer. can do. As a result, a light guiding mechanism with a low light can be formed at the stripe-shaped opening into which an effective refractive index in the direction parallel to the junction is injected, stabilizing the fundamental transverse mode, and reducing the threshold current due to light absorption loss. In addition to suppressing the increase, the wavefront of the guided light is flattened, and a small astigmatic difference indispensable as a laser for an optical disk can be realized.

Also in the above-described structure, the refractive index of the cladding layer between the current injection layer and the active layer and the refractive index of the current block layer, or the refractive index of at least a portion of the current injection layer close to the active layer are determined. By making them approximately equal, it is not necessary to control a delicate difference in refractive index, which facilitates manufacture, and provides a semiconductor laser with high reproducibility and high yield.

According to the present invention, the band gap of at least a portion of the current injection layer close to the active layer is made larger than the band gap corresponding to the emission wavelength of the active layer, and the band gap of the current block layer is made active. It can be smaller than the band gap corresponding to the emission wavelength of the layer. As a result, a high optical waveguide mechanism can be formed at the stripe-shaped opening into which the effective refractive index in the direction parallel to the junction is injected with current, and the absorption loss for higher-order transverse modes can be increased. it can. Therefore, stabilizing the fundamental transverse mode, suppressing the increase in threshold current due to light diffraction loss, flattening the wavefront of guided light, and achieving a small astigmatic difference indispensable as a laser for optical discs. Becomes possible.

On the other hand, in a conventional gallium nitride based semiconductor laser device having a stripe opening in a current block layer, the thickness of a clad layer formed between the active layer and the current block layer is uniform in the bonding direction. In addition, there is a problem that an invalid current which does not contribute to the oscillation is generated due to the spread of the current.

On the other hand, according to the present invention, the current injection layer is formed so as to be in contact with the groove formed in the cladding layer sandwiched between the current injection layer and the active layer in the stripe-shaped opening. In addition, the current can be concentrated at the center of the stripe, and an invalid current due to current spreading can be suppressed. Such a structure can be remarkably performed by making the resistivity of at least a portion of the current injection layer which is in contact with the groove of the cladding layer lower than the resistivity of the cladding layer.

In the above-described structure, the refractive index of at least a portion of the current injection layer close to the active layer is made larger or smaller than the refractive index of the cladding layer, so that the effective refraction in the direction parallel to the junction is achieved. A high or low optical waveguide mechanism can be formed at the portion where the current is injected. This stabilizes the fundamental transverse mode, suppresses the increase in threshold current due to light absorption loss and diffraction loss, flattens the wavefront of guided light, and reduces the small astigmatic difference indispensable for lasers for optical disks. It can be realized.

In the above structure, by controlling the shape of the groove formed in the cladding layer, the width of the current injection and the width of the light guiding mechanism can be individually controlled. By making the groove of the cladding layer V-shaped,
The current can be concentrated at the center. This is useful for making a laser with a low threshold current. Also, by making the bottom of the groove of the cladding layer flat, the width of the current injection and the width of the light guiding mechanism can be made substantially the same. This is effective for producing a laser having a small astigmatic difference. Further, by making the width of the groove of the cladding layer narrower than the width of the stripe-shaped opening, the width of current injection can be made narrower than the width of the optical waveguide mechanism. This promotes absorption in the non-injection portions on both sides of the current injection portion of the active layer, and is effective for forming a supersaturated absorber to produce a low-noise laser causing self-pulsation.

FIG. 20 is a sectional view showing a device structure of a gallium nitride based compound semiconductor laser according to still another embodiment of the present invention. In this embodiment, in the opening of the current constriction structure, the angle between the side wall of the opening and the interface between the current blocking layer 16 and the current injection layer (layer 17 + layer 18) is 45 ° to 90 °. It is characterized by. An embodiment of the method of manufacturing the semiconductor laser shown in FIG.
This will be described with reference to (a) to (c) and FIGS. 22 (a) to (c).

First, a GaN buffer layer 1 was formed on a sapphire substrate 10 by metal organic chemical vapor deposition (MOCVD).
1 is grown to a film thickness of about 10 to 200 nm, and S
An n-contact layer 12 of i-doped GaN was grown to a thickness of 4 μm. Subsequently, n of Si-doped Ga _0.8 Al _0.2 N
A cladding layer 13 was grown with a thickness of 250 nm; Next, a non-doped GaN optical guide layer having a thickness of 200 nm, two types of InGaN layers of a non-doped In _0.25 Ga _0.75 N having a thickness of 1.5 nm and a non-doped In _0.05 Ga _0.95 N having a thickness of 3 nm are formed by repeating 50 periods. The MQW active layer 14 was formed by laminating a multi-quantum well (MQW) structure to be formed and a light guide layer of non-doped GaN having a thickness of 200 nm. Next, Mg-doped Ga _0.8 Al _0.2
A p-cladding layer 15 of N is grown, followed by a thickness of 0.6 μm.
Mg-doped GaN p-etch stop layer 7
2. An n-current blocking layer 16 of Si-doped GaN having a thickness of 1.0 μm was sequentially laminated (FIG. 21A).

Next, as shown in FIG. 21B, a 400 nm-thick SiO ₂ film was deposited as an inorganic material layer 74 on the current blocking layer 16 by a thermal CVD method. Subsequently, a resist layer (AZ4330) 76 was applied to a thickness of 3 μm, and a stripe pattern was transferred by a light exposure process. Next, after the development, the wafer was placed in an oven in a nitrogen atmosphere at 150 ° C. for 20 minutes to perform a resist curing treatment.

In this treatment, the higher the temperature, the more the resist was cured, and the plasma resistance during dry etching was increased. Above 100 ° C., an increase in plasma resistance was observed.
On the other hand, when the temperature was higher, at 250 ° C. or higher, it was difficult to remove the resist after etching. For this reason, the treatment in the range of 100 ° C. to 250 ° C. was effective.

Immediately after the development, the side wall of the resist layer 76 is almost perpendicular to the interface between the resist layer 76 and the current blocking layer 16, but this resist curing treatment causes a reflow phenomenon of the resist, and FIG. As shown, a taper 78 could be formed on the side wall of the mask of the resist layer 76. Due to such a taper of the side wall of the resist,
During the dry etching, the resist layer 76 receded due to sputtering. As a result, as shown in FIG. 22A, a taper 79 could be formed on the side wall of the etched portion of the gallium nitride-based compound semiconductor. The taper 79
Is the temperature at the time of the hardening process of the resist and the resist layer 76.
And the thickness of the inorganic material layer 74.

Using two masks of the inorganic material layer 74 and the resist layer 76 formed as described above, a part of the current block layer 16 is formed by a reactive ion beam etching (RIBE) method using chlorine gas. The etching was performed until the etching stop layer 72 was exposed in a stripe shape. The etching condition of the current blocking layer 16 is a chlorine pressure of 0.4.
mTorr, microwave power 200 W, ion acceleration voltage 500 V. As a result, the width is 5 μm and the depth is 1.7 μm.
With m, an opening having an angle of about 50 ° between the current blocking layer on the etching side wall and the interface of the mask was formed.

After the dry etching, the wafer was treated in a mixed solution of sulfuric acid: hydrogen peroxide: water and then in hydrofluoric acid, and the etching mask was removed as shown in FIG. In addition, 100
After being immersed in a solution of HNO ₃ : HCl = 3: 1 heated to at least 30 ° C. for 30 minutes, it was rinsed with pure water.

After the processing described above, as shown in FIG. 22C, the first p-contact layer 1 of Mg-doped GaN is formed.
7 is 1.0 μm, and the second of p ⁺ -GaN doped with Mg to a higher concentration than the first p-contact layer 17.
The p-contact layer 17 was regrown to a thickness of 0.2 μm by MOCVD.

Next, at a position deviated from the stripe at the opening of the current block layer 16, the n-contact layer 12 was partially etched again by RIBE in parallel with the stripe. As a result, a mesa having a double hetero structure and a current confinement structure was formed, and an n-contact layer 12 was formed next to the mesa. Next, the exposed n-
An n-side electrode 21 is formed on the surface of the contact layer 12,
The p-side electrode 22 was formed on the surface of the contact layer 18. Further, an element separation step was performed to produce the gallium nitride based semiconductor laser element shown in FIG.

FIG. 23 shows a p-contact layer (first and second layers).
A view of the p-contact layers 17 and 18 as one layer (the same applies hereinafter). A scanning electron micrograph of the periphery of the opening after regrowth. As shown, the surface after the regrowth had good flatness. In addition, no deterioration in crystallinity was observed at the interface between the regrown layer and the bottom surface of the opening of the current block layer and at the interface between the regrown layer and the side surface of the current block layer.

According to this manufacturing method, the current blocking layer 1
The angle θ (FIG. 21C) formed between the side wall of the opening 6 and the interface between the upper surface of the current blocking layer 16 and the p-contact layer can be controlled. However, if the angle is too small, the mask will retreat remarkably during dry etching, making it difficult to control the width of the opening of the current blocking layer 16. Further, as shown in FIG. 24, during the first crystal growth or the regrowth step, Mg from the p-GaN etching stop layer 72 or the p-GaN contact layer is introduced into the n-GaN current block layer 16. Diffusion occurs and n-G due to Mg contamination around the growing reaction tube
Mg is taken into the aN layer 16. For this reason,
At the interface between the n-GaN layer 16 and the p-GaN layer, a region of i-GaN or p ⁻ -GaN is formed, and the effective thickness is reduced. Therefore, the current blocking layer 1
When the angle between the side wall of the opening 6 and the interface between the upper surface of the current blocking layer 16 and the contact layer is small, the width of the opening of the n-GaN current blocking layer 16 that can exhibit the current confinement effect becomes wide. At the same time, the controllability of the width also worsens. Therefore, a practical angle is preferably 45 ° or more.

FIGS. 25 (a)-(c) and 26 (a)-
(C) is a figure which shows the example of the manufacturing method of the gallium nitride compound semiconductor laser which concerns on another embodiment of this invention.

In order to enhance the current confinement effect, the width of the opening of the current block layer 16 must be reduced to 3 μm or less. In order to obtain such a narrow opening, the angle of the pattern side wall of the resist layer 76 needs to be close to vertical, and the side wall of the opening of the current block layer formed by dry etching needs to be close to vertical.

First, a laminated structure up to the n-GaN current block layer 16 was grown by the same steps as those described with reference to FIG. 21A (FIG. 25A). Next, FIG.
5 (b) As shown in FIG.
An O ₂ layer 74 was deposited to a thickness of 0.4 μm by thermal CVD. Subsequently, a resist layer (AZ4330) 76 was applied to a thickness of 3 μm. Thereafter, the wafer was placed in an oven in a nitrogen atmosphere at 250 ° C. for 20 minutes to perform a hardening treatment of the resist.

Thereafter, the Ti or Al layer 82 is
Evaporation was performed using a 200 nm electron beam evaporation apparatus. Further, a resist layer (AZ4110) 84 was applied to a thickness of 1 μm, and a stripe pattern was transferred to the resist layer 84 by a light exposure process (FIG. 25C). After the development, the Ti or Al layer 82 was etched by reactive ion beam etching using chlorine gas to form a stripe pattern (FIG. 26A). Furthermore, RIB using oxygen gas
E, the resist layer 76 was etched using the Ti or Al layer 82 as a mask to transfer the stripe pattern (FIG. 26B).

By this step, a resist layer 76 having substantially vertical side walls could be manufactured. Resist layer 7
Sample No. 6 had already been subjected to the resist curing treatment at 250 ° C., and thus had good resistance to chlorine plasma. SiO
After selectively etching away the _second layer 74, it was etched opening of the current blocking layer 16 by a two-layer mask of the resist layer 76 and the SiO ₂ layer 74. As a result, an opening of the current block layer 16 having a width of 1 μm and a vertical side wall was formed.

According to the embodiment described with reference to FIGS. 20 to 26, the following effects can be obtained. First, even if the contact layer 17 to be regrown is thin, the opening of the current block layer 16 can be buried flat. In addition, crystallinity degradation at the interface between the bottom surface of the opening of the current block layer 16 and the regrown contact layer 17 and at the interface between the side surface of the opening and the regrown contact layer 17 can be suppressed. Therefore, leakage current at these interfaces can be suppressed, and current can be constricted and current can be uniformly injected into the active layer. Therefore, it is possible to lower the threshold value and improve the reliability. Therefore, it is possible to realize a highly reliable gallium nitride-based compound semiconductor laser that is practically used for an optical disk or the like.

FIGS. 27A to 27C are diagrams showing an example of a method for manufacturing a gallium nitride-based compound semiconductor laser according to still another embodiment of the present invention. 21A to 21C and FIG. 22A.
Since it is substantially the same as that described with reference to (c), only its outline will be described.

First, on the sapphire substrate 10, a buffer layer 11 of GaN having a thickness of about 10 to 200 nm and an n-contact layer 1 of Si-doped n-GaN having a thickness of 4 μm are provided.
2. Si-doped n-Ga _0.8 Al _0.2 N n-cladding layer 13 having a thickness of 250 nm, MQW active layer 1 having a multilayer structure
4. Mg-doped Ga _0.8 Al _0.2 N p-clad layer 1
5, Mg-doped GaN p-etch stop layer 72 with a thickness of 0.6 μm, Si-doped GaN with a thickness of 1.0 μm
27 were sequentially laminated (FIG. 27).
(A)).

Next, a thickness of 400
A SiO ₂ inorganic material layer 74 nm and a resist layer (AZ4330) 76 having a thickness of 3 μm were formed. After the stripe pattern was transferred to the resist layer 76 by a light exposure process, the developed wafer was placed in an oven in a nitrogen atmosphere at 150 ° C. for 20 minutes to cure the resist. This resist curing process causes a reflow phenomenon of the resist,
The side wall of the resist layer 76 could be tapered.

In the etching of a gallium nitride-based compound semiconductor, the selectivity with respect to a resist mask is as small as approximately 1. For this reason, when the side wall of the mask of the resist layer 76 has a taper, the mask recedes due to the etching.
A taper can be formed on the side wall of the etched portion of the gallium nitride-based compound semiconductor. The angle of this taper can be controlled by the temperature at the time of the resist curing process and the thickness of the resist layer 76 and the inorganic material layer 74. Note that the inorganic mask layer does not need to be SiO ₂ and may use SiNx.

Using the two-layer mask of the inorganic material layer 74 and the resist layer 76 formed as described above, a part of the current block layer 16 is formed by a reactive ion beam etching (RIBE) method using chlorine gas. The etching was performed until the etching stop layer 72 was exposed in a stripe shape. As a result, the width of 5 μm, the depth of 1.7 μm, and the angle between the interface between the current blocking layer on the etching side wall and the mask was about 5
An opening 77 of 0 ° was produced (FIG. 27B).

After the dry etching, the wafer was treated in a mixed solution of sulfuric acid: hydrogen peroxide: water and then in hydrofluoric acid to remove the etching mask. HNO ₃ further heated to 100 ° C. or higher:
After being immersed in a solution of HCl = 3: 1 for 30 minutes, it was rinsed with pure water. HNO ₃ : HCl =
By immersing in a 3: 1 solution for 30 minutes, the opening 77
And etching the surface of the current block layer 16 by about 4 nm,
An etching residue due to dry etching and a damaged layer in the crystal were removed. There was no morphological deterioration due to this processing, and good embedding was possible as described later.

Usually, KO is used as an etchant for GaN.
H and NaOH are known, but in etching using these, for example, M.H. S. Minsky et al. (Appl.
Phys. Lett. Vol. 68 No. 11 (19
96) p. 1531), the morphology is significantly degraded, and good regrowth is considered impossible. The HNO ₃ : HCl used in the present invention
= 3: 1 solution was obtained from S.I. J. Pearton et al. (Mate
reals Science and Engineer
ring B31 (1995) p. 309), it is conventionally said that GaN is not etched.

On the other hand, the present invention relates to HNO ₃ : HC
By heating the l = 3: 1 solution above 100 ° C.,
It has been found that GaN is etched at an etching rate of about 0.13 nm / min, and is applied to a manufacturing process of a gallium nitride-based compound semiconductor laser. As a result, the morphology is not degraded, and the amount of etching can be controlled very finely.In the regrowth step, dislocations are introduced at the interface due to the rough homology of the interface, and the surface of the regrown layer is formed. No rough morphology was observed.

After the above-described processing, as shown in FIG. 27C, the Mg-doped GaN p- first contact layer 17 and the Mg-doped p-type p-type contact layer 17 have a higher concentration than the first contact layer 17. ⁺ -GaN second contact layer 1
8 was regrown by MOCVD.

Next, RI is again performed up to the n-contact layer 12.
BE was partially etched to form a mesa having a double hetero structure and a current confinement structure, and an n-contact layer 12 was formed on the side of the mesa. Next, an n-side electrode 21 was formed on the exposed surface of the n-contact layer 12, and a p-side electrode 22 was formed on the surface of the p-contact layer 18. Further, an element separation step was performed to produce the gallium nitride based semiconductor laser element shown in FIG.

FIG. 23 shows a p-contact layer (first and second layers).
A view of the contact layers 17 and 18 as one layer (the same applies hereinafter). A scanning electron microscope photograph around the opening after regrowth is shown. As shown, the surface after the regrowth had good flatness.

FIG. 28A is an enlarged view around the opening 77 after the regrowth of the p-contact layer. FIG.
(B) shows the relationship between the width W1 of the upper part of the opening 77 formed by dry etching and the depth d4 of the groove on the surface of the p-contact layer after regrowth, using the depth d1 of the opening 77 as a variable. FIG. That is, FIG. 28B shows the dependence of the flatness of the surface of the p-contact layer on the width W1 and the depth d1 of the opening 77.

The thickness d2 of the regrown contact layer is 1.
In the case of 2 μm, when the depth d1 of the opening 77 is 2.3 μm, the width W1 of the opening 77 is 5 μm or less and is buried flat.
When the depth d1 was 1.6 μm, the width W1 was 7.5 μm or less, and the surface was buried flat. That is, when the width W1 of the opening is narrow, it is possible to bury the regrowth layer even with a thickness smaller than the depth d1 of the opening. On the other hand, when the width W1 of the opening was large, a V-shaped groove (depth d4) was formed on the surface after the regrowth and was not buried flat.

In order to bury the opening 77 flat with the regrowth layer, the growth rate of the regrown layer in the opening 77 is higher than the growth rate in the non-opening part, and the growth rate is d2 in the direction perpendicular to the wafer in the non-opening part. During this time, a portion corresponding to the volume of the opening 77 needs to be buried extra. In MOCVD of a gallium nitride-based compound semiconductor, the contribution of surface diffusion is large, so that the raw material is supplied from the non-opening to the opening by surface diffusion. The speed at which the raw material is taken into the opening side wall of the current blocking layer 16 depends on the current blocking layer 1.
6 is faster than the top surface. For example, the thickness d2 of the regrown contact layer is 1.2 μm, and the depth d1 of the opening is 1.6 μm.
In the case of, lateral growth on the side wall of the opening 77 occurred at about 4.5 μm. That is, the growth rate in the opening 77 is higher than that in the non-opening part. If the difference in the growth rate can compensate for the portion corresponding to the volume of the opening of the current block layer, it can be buried flat. is there.

Here, the width of the lower portion of the opening 77 is set to W
2. Assuming that the length of the stripe of the opening 77 is L, while growing the contact layer by the thickness d2, about 2 × (4.5 × 1.6) × d2 / 1 at the opening of the current block layer. .2
It is buried more than the non-opening portion by × L. When the cross section of the opening of the current block layer is approximated by a trapezoid, the volume of the opening is (W1 + W2) × d1 / 2 × L. Therefore, if (12 × d2 × L ≧ (w1 + w2) × d1 / 2 × L), that is, (W1 + W2) × d1 / d2 ≦ 24 (11), smooth embedding can be performed. In this formula,
If the thickness of d2, that is, the p-contact layer is increased, a flat filling is always possible. However, the contact layer, ie, p-
Since the GaN layer has a large resistance, if it is too thick,
As a result, the device resistance is increased, and the device characteristics of the current confinement structure are canceled out, thereby deteriorating the device characteristics. Therefore, it is desirable that the thickness d2 of the p-GaN contact layer be equal to or less than the depth of the opening 77 of the current block layer 16. That is, it is desirable that d2 ≦ d1 (12) is satisfied.

According to the embodiment described with reference to FIGS. 27A to 27C, the opening 77 of the current block layer 16 is formed.
Can be buried completely flat without increasing the thickness of the p-contact layer, so that the element resistance does not increase. In addition, since an effective current constriction effect by the current blocking layer 16 is obtained, uniform and efficient injection of current into the active layer 14 becomes possible.

FIG. 29 is a sectional view showing a device structure of a gallium nitride based compound semiconductor laser according to still another embodiment of the present invention. An embodiment of the method of manufacturing the semiconductor laser shown in FIG. 29 will be described with reference to FIGS.

This embodiment is different from the embodiment shown in FIGS.
The difference from this embodiment is that InGaN is used as the etching stop layer 72 in forming the opening 77 of the current block layer 16. The steps up to the middle of this embodiment are the same as those of the embodiment shown in FIGS.

In this embodiment, an etching stop layer 72 made of non-doped In _0.15 Ga _0.85 N is grown on the p-cladding layer 15 by 0.2 μm, followed by n-Ga
The N current blocking layer 16 was grown 1.5 μm (FIG. 30)
(A)).

Thereafter, an SiO ₂ layer 74 was deposited to a thickness of 0.3 μm by a thermal CVD method, and a resist layer 76 was applied. Light exposure and development were performed to form a stripe pattern.
Next, the resist was heated to 150 ° C. in an oven in a nitrogen atmosphere to cure the resist. Subsequently, a part of the current block layer 16 was etched by reactive ion beam etching until the etching stop layer 72 made of non-doped In _0.15 Ga _0.85 N was exposed to form an opening 77. Thereafter, the wafer was immersed in a mixed solution of sulfuric acid: hydrogen peroxide: water and then in hydrofluoric acid to remove the resist layer 76 and the SiO ₂ layer 74 serving as an etching mask (FIG. 30B).

Next, it is put again in the growth apparatus, and nitrogen gas,
By exposing to a temperature higher than 900 ° C. in an atmosphere containing hydrogen gas as a main component in addition to ammonia gas, the In _0.15 Ga _0.85 N layer serving as the etching stop layer 72 is evaporated, and the surface of the clean p-cladding layer 15 and A current block layer surface was obtained. Next, on the current blocking layer 16 and the exposed p-cladding layer 15, the first p-
The contact layer 17 and the second p-contact layer 18 of p ⁺ -GaN were sequentially grown (FIG. 30C). After that,
By performing the same steps as in the manufacturing method of FIGS. 27A to 27C, the gallium nitride-based compound semiconductor laser shown in FIG. 29 was manufactured.

In this manufacturing method, the distance from the top of the current blocking layer 16 to the top of the p-cladding layer 15 in the opening 77 is d1, the thickness of the re-grown p-contact layer (layer 17 + layer 18) is d2, Assuming that the width of the upper part of the opening 77 is W1 and the width of the lower part is W2, the opening 77 of the current block layer 16 is designed to satisfy (W1 + W2) × d1 / d2 ≦ 24 (11), thereby achieving smoothness. Can be embedded in Also,
In order to reduce the device resistance, it is necessary to reduce the thickness of the p-GaN contact layer, and it is desirable that the thickness be equal to or less than the depth of the opening 77. That is, it is desirable that d2 ≦ d1 (12) is satisfied.

According to the embodiment described with reference to FIGS. 29 and 30A to 30C, a clean interface can be obtained because the InGaN etching stop layer 72 damaged by dry etching is removed. In addition, the leakage current at the interface can be reduced. Also, the p-cladding layer 15
Since the p-GaN contact layer can be formed directly on the substrate, the effective thickness of p-GaN at the opening of the current block layer can be reduced, and the element resistance can be reduced.

FIG. 31 is a sectional view showing a device structure of a gallium nitride based compound semiconductor laser according to still another embodiment of the present invention. An embodiment of the method of manufacturing the semiconductor laser shown in FIG. 31 will be described with reference to FIGS.

This embodiment is different from the embodiment shown in FIGS.
The difference from this embodiment is that there is no etching stop layer 72 in forming the opening 77 of the current blocking layer 16. Until the process in the middle of this embodiment, FIG.
7 (a) to 7 (c) are the same as those in the embodiment, so that the details are omitted.

In the present embodiment, the n-GaN current blocking layer 16 is grown 1.5 μm directly on the p-cladding layer 15 (FIG. 32A).

Thereafter, an SiO ₂ layer 74 was deposited to a thickness of 0.3 μm by a thermal CVD method, and a resist layer 76 was applied. Light exposure and development were performed to form a stripe pattern.
Next, the resist was heated to 150 ° C. in an oven in a nitrogen atmosphere to cure the resist. Subsequently, a part of the current blocking layer 16 was etched by reactive ion beam etching until the p-cladding layer 15 was exposed to form an opening 77. After that, the wafer is mixed with sulfuric acid: hydrogen peroxide: water,
Next, the resist layer 76 and the SiO ₂ layer 74 serving as an etching mask were removed by immersion in hydrofluoric acid (FIG. 32B).

Further, HNO ₃ heated to 100 ° C. or more:
After being immersed in a solution of HCl = 3: 1 for 30 minutes, it was rinsed with pure water. HNO ₃ : HCl =
By immersing in a 3: 1 solution for 30 minutes, the opening and the surface of the current block layer were etched by about 4 nm, and the etching residue by dry etching and the damaged layer in the crystal were removed.

Next, the substrate is put again in the growth apparatus, and Mg is deposited on the current block layer 16 and the exposed p-cladding layer 15.
Doped GaN first p-contact layer 17 and p ⁺ -G
The second p-contact layer 18 of aN was sequentially grown (FIG.
2 (c)). After that, the same steps as those in the manufacturing method of FIGS. 27A to 27C were performed to produce the gallium nitride-based compound semiconductor laser shown in FIG.

In this manufacturing method, the current blocking layer 1
6 has the same depth d1 as the thickness of the current blocking layer 16. Regrown p-contact layer (layer 17)
+ Layer 18) has a thickness of d2 and an upper portion of opening 77 has a width of W
1. Assuming that the width of the lower portion is W2, the opening 77 of the current block layer 16 can be buried smoothly by designing the opening 77 of the current block layer 16 so as to satisfy (W1 + W2) × d1 / d2 ≦ 24 (11). Also,
In order to reduce the device resistance, it is necessary to reduce the thickness of the p-GaN contact layer, and it is desirable that the thickness be equal to or less than the depth of the opening 77. That is, it is desirable that d2 ≦ d1 (12) is satisfied.

According to the embodiment described with reference to FIGS. 31 and 32 (a) to (c), it is necessary to stop dry etching at the interface between p-cladding layer 15 and current blocking layer 16. There are some difficulties in the process.
However, sacrifice of light confinement efficiency and the like can be suppressed by designing the p-cladding layer 15 in consideration of overetching. Further, since a p-GaN contact layer can be directly formed on the p-cladding layer 15,
The effective thickness of p-GaN at the opening 77 of the current block layer 16 can be reduced, and the element resistance can be reduced.

FIG. 33 is a sectional view showing a device structure of a gallium nitride based compound semiconductor laser according to still another embodiment of the present invention.

In this embodiment, the V-shaped groove 8 is formed on the surface of the contact layer above the opening 77 of the current block layer 16.
6 is formed. Therefore, the depth of the opening 77 of the current blocking layer 16 is d1, the thickness of the contact layer (layer 17 + layer 18) to be regrown is d2, the upper width of the opening 77 is W1, and the lower width is W2. Then, if the opening of the current block layer is designed to satisfy 24 <(W1 + W2) × d1 / d2 (13),
A V-shaped groove is formed on the surface of the contact layer above the opening. Further, in order to reduce the element resistance, it is necessary to reduce the thickness of the p-GaN contact layer, and it is preferable that the thickness be equal to or less than the depth of the opening 77. That is, it is desirable that d2 ≦ d1 (12) is satisfied.

Next, an embodiment of a method of manufacturing the semiconductor laser shown in FIG. 33 will be described with reference to FIGS. In addition, up to the process in the middle of this embodiment,
Since the configuration is the same as that of the embodiment shown in FIGS.

First, an n-GaN current block layer 16 was grown by MOCVD (FIG. 34A).

Thereafter, a SiO ₂ layer 74 was deposited to a thickness of 0.3 μm by thermal CVD, and a resist layer 76 was applied. Light exposure and development were performed to form a stripe pattern.
Next, the resist was heated to 150 ° C. in an oven in a nitrogen atmosphere to cure the resist. Subsequently, a part of the current blocking layer 16 is p-G by reactive ion beam etching.
The opening 77 was formed by etching until the aN etching stop layer 72 was exposed. Thereafter, the wafer was immersed in a mixed solution of sulfuric acid: hydrogen peroxide: water and then in hydrofluoric acid to remove the resist layer 76 and the SiO ₂ layer 74 serving as an etching mask (FIG. 34B).

Further, HNO ₃ heated to 100 ° C. or more:
After being immersed in a solution of HCl = 3: 1 for 30 minutes, it was rinsed with pure water. HNO ₃ : HCl =
By immersing in a 3: 1 solution for 30 minutes, the opening and the surface of the current block layer were etched by about 4 nm, and the etching residue by dry etching and the damaged layer in the crystal were removed.

Next, the substrate is put again in the growth apparatus, and the first p-contact layer 17 of Mg-doped GaN and the second p-layer of p ⁺ -GaN are formed on the current block layer 16 and the exposed p-GaN etching stop layer 72. The contact layers 18 were sequentially grown (FIG. 34C). After that, FIG.
By performing the same steps as in the manufacturing methods of (c) to (c), the gallium nitride-based compound semiconductor laser shown in FIG.

In this embodiment, the current blocking layer 1
6 has a width W1 of 12 μm and a depth d1 of 2.3.
μm, p-GaN contact layer (layer 17 + layer 18)
Was regrown with a thickness d2 of 1.2 μm. As a result, FIG.
5, a V-shaped groove 86 having a width of 4 μm and a depth of 2 μm can be formed on the surface of the p-GaN contact layer above the opening 77 of the current block layer 16. Was.

When the p-side electrode 22 is formed so as to cover the V-shaped groove 86, the contact resistance between the side surface of the groove 86 and the electrode 22 becomes lower than the contact resistance on the surface of the contact layer. The resistance could be reduced. In addition, since the injection current can have a distribution that maximizes the injection from the groove bottom,
A more efficient current narrowing effect can be expected than the narrowing effect of only the current blocking layer. In the embodiment of FIGS. 34A to 34C, p-G is used as the etching stop layer 72.
Although the case of using aN has been described, as in the other embodiments, InGaN is used as the etching stop layer 72.
This embodiment can be applied to the case where the etching stop layer 72 is not used. FIG. 36 shows a completed device structure when InGaN is used as the etching stop layer 72, and FIG. 37 shows a completed device structure when the etching stop layer 72 is not used.

Next, still another embodiment of the present invention will be described with reference to FIGS. In these embodiments, oxygen (O) is introduced (ion-implanted or diffused) into at least a part of the Mg-doped hexagonal p-type semiconductor layer, so that the p region and the i region coexist in the same plane. It is characterized in that a structure is formed.

A Group III nitride compound semiconductor such as GaN is
Since the material is hard, processing is performed using dry etching. At this time, there is a problem that a semiconductor layer such as an active layer is damaged by the reactive gas. Therefore, in these embodiments, by introducing O into a part of the Mg-doped p-type semiconductor layer, MgO is introduced into the p-type semiconductor layer.
To form Accordingly, a structure in which the p region and the i region are mixed in the same plane can be formed without performing processes such as etching and regrowth.

Typically, as described later, Mg-doped G
aAlN p-clad layer 15 and Mg-doped GaN p-clad layer 15
-By introducing O into a part of the contact layer 92 (layer 17 + layer 18), the current blocking layers 93 and 94 having high resistance are introduced.
Is formed, a current confinement structure can be formed. The current block layers 93 and 94 formed in this way are made of Mg.
Since O is contained, a difference in the refractive index with respect to the original layer appears, and an effect is also exhibited regarding light confinement. Therefore, a semiconductor laser device having a low oscillation threshold and a controlled mode can be obtained.

In the semiconductor laser of the embodiment shown in FIG. 38, an undoped GaN buffer layer 11 and a Si-doped G layer are formed on a hexagonal substrate, for example, a sapphire substrate 10.
aN n-contact layer 12, Si-doped GaAlN n-clad layer 13, active layer 14, Mg-doped GaAl
N-p-cladding layer 15 and Mg-doped low-resistance GaN
Are sequentially stacked. Active layer 14
Are undoped GaN light guide layers 14a, InGaN
/ InGaN has a laminated structure of a quantum well layer 14b and a p-GaN optical guide layer 14c.

Mg-doped GaN p-contact layer 92
Is partially ion-implanted with O and heat-treated to form a high-resistance GaN current block layer 94. The current block layer 94 has a stripe-shaped opening having a width of 3 μm, thereby forming a current confinement structure. The n-side electrode 21 is disposed on the exposed surface of the n-contact layer 12 from the p-contact layer 92 to the middle of the n-contact layer 12. Is provided with a p-side electrode 22. The laser threshold of this structure is 1 kA / c
m ^2, which is 1/5 or less of the conventional value.

In the semiconductor laser of the embodiment shown in FIG. 39, a hexagonal crystal substrate, for example, a SiC substrate 90 is
An n-contact layer 12 of Si-doped GaN, an n-cladding layer 13 of Si-doped GaAlN, an active layer 14 having the same structure as the embodiment shown in FIG. 38, a p-cladding layer 15 of Mg-doped GaAlN, and a Mg-doped low resistance GaN p
-The contact layers 92 are sequentially stacked.

Mg-doped GaAlN p-clad layer 1
5 and Mg-doped GaN p-contact layers 92 include:
By partially implanting O and performing heat treatment, a high-resistance GaAlN current block layer 93 and a high-resistance GaN current block layer 94 are formed. Each of the current blocking layers 93 and 94 has a stripe-shaped opening having a width of 3 μm, thereby forming a current confinement structure. The n-side electrode 21 is disposed on the exposed surface of the n-contact layer 12 from the p-contact layer 92 to the middle of the n-contact layer 12.
On the surface of the contact layer 92, the p-side electrode 22 is provided. The threshold value of the laser having this structure is 1 kA / cm ^2, which is 1/5 or less of the conventional value.

The embodiment shown in FIG. 40 is similar to the embodiment shown in FIG. 39, except that the n-side electrode 21 is provided on the back surface of the substrate 90 made of SiC.

The embodiment shown in FIG. 41 is similar to the embodiment shown in FIG.
Extend to the interface between the p-cladding layer 15 and the p-contact layer 92.

The embodiment shown in FIG. 42 is a combination of the two embodiments shown in FIGS. 39 and 41, and uses the sapphire substrate 10 as the substrate. Mg-doped GaAlN p-clad layer 15 and Mg-doped GaN
O is partially ion-implanted into the p-contact layer 92 and is subjected to a heat treatment so that the high-resistance GaAs
An 1N current block layer 93 and a high resistance GaN current block layer 94 are formed.

Next, still another embodiment of the present invention will be described with reference to FIGS. In these embodiments, oxygen (O) is introduced (ion-implanted or diffused) into at least a part of a hexagonal semiconductor layer containing Al as a constituent element, so that a low-resistance region and a high-resistance region are formed in the same plane. It is characterized in that a structure in which regions are mixed is formed.

A Group III nitride compound semiconductor such as GaN is
Since the material is hard, processing is performed using dry etching. For this reason, there is a problem that it is difficult to form an element structure that requires fine processing. Therefore, in these embodiments, by introducing O into a part of the semiconductor layer containing Al as a constituent element, Al _x
To form an O _y. Thus, a structure in which a low-resistance region and a high-resistance region are mixed in the same plane can be formed without performing processes such as etching and regrowth. In particular, in the case of a planar element, it is possible to further introduce a refractive index difference and a current confinement in the microcavity, thereby greatly improving the performance. For example, a laser can be expected to greatly reduce the oscillation threshold. .

Typically, as described later, GaAlN
Some of the layers such as the n- and p-cladding layers 13 and 15
, The high-resistance current blocking layer 106
Is formed, a current confinement structure can be formed. The current block layer 106 thus formed is made of Al _x O
_Since it contains _y , it becomes the part with the lowest refractive index in the layer,
It also shows an effect on light confinement. Therefore, a semiconductor laser device having a low oscillation threshold and a controlled mode can be obtained.

In the semiconductor laser of the embodiment shown in FIG. 43, an undoped GaN buffer layer 11 and a Si-doped G layer are formed on a hexagonal substrate, for example, a sapphire substrate 10.
aN n-contact layer 12, GaN / GaAlN
A reflector layer 102, a Si-doped GaAlN n-clad layer 13, an active layer 14, a Mg-doped GaAlN p-clad layer 15, a GaN / GaAlN p-reflector layer 10.
4, and Mg-doped low-resistance GaN p-contact layer 9
2 are sequentially stacked. The active layer 14 is made of undoped GaN
, An InGaN / InGaN quantum well layer 14b, and a p-GaN layer 14c.

The n- and p-cladding layers 13, 15 and n-
A high-resistance current block layer 106 containing Al _x O _y is formed by partially ion-implanting O into the p-reflecting mirror layers 102 and 104. The current block layer 106 is formed on the outer periphery of the current injection region having a diameter of 3 μm, thereby forming a current confinement structure. Further, the n-contact layer 1 is partially etched and partially exposed from the p-contact layer 92 to the middle of the n-contact layer 12.
The n-side electrode 21 is provided on the surface of the second substrate 2, and the p-side electrode 22 is provided on the surface of the p-contact layer 92. The laser having this structure is a so-called surface emitting laser that emits light in the stacking direction, and has a threshold of 0.3 kA / cm ^2.
Which is 1/5 or less of the conventional value.

In the semiconductor laser of the embodiment shown in FIG. 44, a hexagonal substrate, for example, a SiC substrate 90 is
43. Si-doped GaN n-contact layer 12, Si-doped GaAlN n-clad layer 13, active layer 14 having the same structure as in the embodiment shown in FIG. 43, Mg-doped GaAlN p-clad layer 15, Mg-doped low-resistance GaN Are sequentially stacked. The substrate 90 is partially etched from the back surface and the exposed n-contact layer 1 is exposed.
2 on the surface of P.2 and on the upper surface of the p-contact layer 92.
/ TiO reflecting mirror layers 108, 108 are provided respectively.

In the n- and p-cladding layers 13 and 15,
By partially ion-implanting O, Al _x O _y
Is formed. The current block layer 106 is formed on the outer periphery of the current injection region having a diameter of 3 μm, thereby forming a current confinement structure. The n-side electrode 21 is provided on the back surface of the SiC substrate 90, and the p-side electrode 22 is provided on the top surface of the p-contact layer 92. The threshold value of the surface emitting laser having this structure is 1
kA / cm ^2, which is 1/5 or less of the conventional value.

In the semiconductor laser of the embodiment shown in FIG. 45, an undoped GaN buffer layer 11 and a Si-doped G layer are formed on a hexagonal substrate, for example, a sapphire substrate 10.
aN n-contact layer 12, Si-doped GaAlN n-clad layer 13, active layer 14 having the same structure as in the embodiment shown in FIG. 43, Mg-doped GaAlN p-clad layer 15, and Mg-doped low-resistance GaN The p-contact layers 92 are sequentially stacked.

The p-clad layer 15 is partially ion-implanted with O to form a high-resistance current block layer 106 containing Al _x O _y . Current block layer 1
Reference numeral 06 has a stripe-shaped opening having a width of 3 μm, thereby forming a current confinement structure. The n-side electrode 21 is disposed on the exposed surface of the n-contact layer 12 from the p-contact layer 92 to the middle of the n-contact layer 12. Is provided with a p-side electrode 22. The threshold value of the laser having this structure is 1 kA / cm ^2, which is 1/5 or less of the conventional value.

In the semiconductor laser of the embodiment shown in FIG. 46, for example, an AlG
aAs / AlGaAs / AlAs / AlGaAs / Al
GaAs n-DBR (Distributed Bragg Reflector
) Layer 112, n-clad layer 113 of AlGaAs,
An active layer 114, an AlGaAs p-clad layer 115,
AlGaAs / AlGaAs / AlAs / AlGaAs
/ AlGaAs p-DBR layer 117, GaAs p-DBR layer 117
The contact layers 118 are sequentially stacked. Active layer 114
Are undoped GaAs light guide layers 114a, AlG
aAs / GaAs quantum well layer 114b and p-Ga
It has a laminated structure of the As light guide layer 114c.

P-Clad Layer 115 and p-DBR Layer 1
17 is partially ion-implanted with O,
A high resistance current block layer 116 containing Al _x O _y is formed. The current blocking layer 116 is formed on the outer periphery of the current injection region having a diameter of 3 μm, thereby forming a current confinement structure. An n-side electrode 121 is provided on the back surface of the GaAs substrate 110, and a p-side electrode 122 is provided on the upper surface of the p-contact layer 118. The threshold value of the surface emitting laser having this structure is 1 kA / cm ^2, which is 1/5
It is as follows.

Next, still another embodiment of the present invention will be described with reference to FIGS. In these embodiments, an impurity is introduced into at least a part of the hexagonal semiconductor layer to form a structure in which any two of the p region, the n region, and the i region are mixed in the same plane. Features.

A Group III nitride compound semiconductor such as GaN is
Since the material is hard, processing is performed using dry etching. At this time, there is a problem that a semiconductor layer such as an active layer is damaged by the reactive gas. Therefore, in these embodiments, an impurity is introduced into at least a part of the semiconductor layer. As a result, a structure in which any two of the p region, the n region, and the i region coexist in the same plane can be formed without performing processes such as etching and regrowth. This makes it possible to form, for example, a current confinement structure, an electrode lead portion, and the like.

In the Mg-doped p-type semiconductor layer, carriers increase as the temperature rises. On the other hand, by introducing impurities (ion implantation or diffusion) and providing a heat generating layer, heat can be locally generated during operation, so that a semiconductor laser device having a low oscillation threshold can be obtained. Further, by using the heat generating layer, sufficient carriers are generated, and a light receiving element particularly suitable for receiving light in an ultraviolet region can be obtained.

In the semiconductor laser of the embodiment shown in FIG. 47, a buffer layer 11 of undoped GaN and a Si-doped G layer are formed on a hexagonal substrate, for example, a sapphire substrate 10.
aN n-contact layer 12, Si-doped GaAlN n-cladding layer 13, active layer 14, Mg-doped Ga
AlN p-cladding layers 15 are sequentially stacked. The active layer 14 includes an undoped GaN light guide layer 14a, InG
aN / InGaN quantum well layer 14b and p-GaN
Of the light guide layer 14c.

On the p-cladding layer 15, a low-resistance GaN
P-layer 131, high-resistance GaN current blocking layer 13
2. High resistance GaN p-layer 133, GaN p-layer 13
4. A GaN p-contact layer 135 is sequentially stacked. The current block layer 132 has a stripe-shaped opening having a width of 3 μm, thereby forming a current confinement structure.

Si is partially ion-implanted as an impurity so as to extend from the p-contact layer 135 to the n-contact layer 12 beyond the n-cladding layer 13 so that the low-resistance n
-An electrode extraction layer 136 is formed. The n-side electrode 21 is provided on the surface of the n-electrode extraction layer 136, and the p-side electrode 22 is provided on the surface of the p-contact layer 135. The threshold value of the laser of this structure is 1 kA / cm ² ,
It is 1/5 or less of the conventional one.

In the semiconductor laser of the embodiment shown in FIG. 48, an undoped GaN buffer layer 11 and a Si-doped G layer are formed on a hexagonal substrate, for example, a sapphire substrate 10.
aN n-contact layer 12, Si-doped GaAlN n-clad layer 13, active layer 14 having the same structure as in the embodiment shown in FIG. 47, Mg-doped GaAlN p-clad layer 15, Mg-doped GaN p-current An injection layer 17 and a p-contact layer 18 of Mg-doped low-resistance GaN are sequentially stacked.

A current blocking layer 137 of high-resistance GaN is formed in the p-current injection layer 17 by partially ion-implanting Si. The current block layer 137 is 3
It has a stripe-shaped opening with a width of μm, whereby a current confinement structure is created. The n-side electrode 21 is disposed on the exposed surface of the n-contact layer 12 from the p-contact layer 18 to the middle of the n-contact layer 12. Is provided with a p-side electrode 22. The threshold value of the laser having this structure is 1 kA / cm ^2, which is 1/5 or less of the conventional value.

In the semiconductor laser according to the embodiment shown in FIG. 49, an undoped GaN buffer layer 11 and a Si-doped GaN buffer layer 11 are formed on a hexagonal substrate, for example, a sapphire substrate 10.
An n-contact layer 12 of aN, an n-cladding layer 13 of Si-doped GaAlN, an active layer 14 having the same structure as the embodiment shown in FIG. 47, and a p-cladding layer 15 of Mg-doped GaAlN are sequentially laminated.

On the p-cladding layer 15, a low-resistance GaN
P-layer 141, a low-resistance GaN p-layer 144, and G
An aN p-contact layer 145 is sequentially stacked. A current blocking layer 142 of high-resistance GaN is formed in the p-layer 141 of low-resistance GaN by partially diffusing and introducing Si as an impurity. Current block layer 142
Has a stripe-shaped opening having a width of 3 μm, thereby forming a current confinement structure. In addition, the p-
In the surface of the layer 141, Si is diffused and introduced as an impurity over the entire surface, so that the p- layer 143 of high resistance GaN is formed.
Is formed. From the p-contact layer 145 to the n-contact layer 12 beyond the n-cladding layer 13,
Si is partially ion-implanted as an impurity to form a low-resistance n-electrode extraction layer 146. The n-side electrode 21 is provided on the surface of the n-electrode extraction layer 146, and the p-side electrode 22 is provided on the surface of the p-contact layer 135.
The threshold value of the laser having this structure is 1 kA / cm ^2, which is 1/5 or less of the conventional value.

In the semiconductor light receiving device of the embodiment shown in FIG. 50, a hexagonal substrate, for example, a sapphire substrate 15
0, undoped GaN buffer layer 151, GaN
N-contact layer 152, low-resistance GaN p-layer 15
4 and a GaN p-contact layer 156 are sequentially stacked. By partially introducing impurities into the surface of n-contact layer 152, high-resistance GaN current block layer 153 is formed. By introducing impurities into the surface of the p- layer 154, a heating layer 155 of high resistance GaN is formed.

An n-side electrode 157 is provided on the exposed surface of the n-contact layer 152 by partially etching the p-contact layer 156 to the middle of the n-contact layer 152. A p-side electrode 158 is provided on the surface of 156. According to this structure, heat can be locally generated during operation by the heat generating layer 155, so that sufficient carriers can be supplied.

Although the above-described embodiments show specific materials, compositions, thicknesses, and the like, these can be changed within the scope of the present invention. In particular, the gallium nitride-based compound semiconductor, an In _x Ga _y Al
_{z N (x + y + z} = 1,0 ≦ x, y, z ≦ 1) can be variously modified within the composition formula. Further, as the supporting substrate, in addition to the sapphire substrate, SiC, GaAs, S
i, GaN, AlN, MgO, GaP, MgAl ₂ O ₄
Etc. can be used.

In the embodiments described above, examples in which the present invention is mainly applied to a semiconductor laser have been described. However, the present invention is not limited to a semiconductor laser, but may be applied to various semiconductor devices using a gallium nitride-based compound semiconductor material. Is also possible. In addition, various modifications can be made without departing from the scope of the present invention.

[0268]

According to the present invention, a carrier can be efficiently injected into an active layer and a voltage drop at an electrode contact or the like can be suppressed. A gallium nitride-based compound semiconductor laser that operates at low voltage and has high reliability can be realized.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an element structure of a gallium nitride-based compound semiconductor laser according to an embodiment of the present invention.

2A to 2C are cross-sectional views illustrating a first half of a method of manufacturing the semiconductor laser illustrated in FIG.

FIGS. 3A and 3B are cross-sectional views showing the latter half of the method of manufacturing the semiconductor laser shown in FIG. 1;

FIG. 4 is a sectional view showing a mounted state of the semiconductor laser shown in FIG. 1;

FIG. 5 is a sectional view showing a device structure of a gallium nitride-based compound semiconductor laser according to another embodiment of the present invention.

6A to 6C are cross-sectional views illustrating a method for manufacturing the semiconductor laser illustrated in FIG.

FIG. 7 is a sectional view showing an element structure of a gallium nitride-based compound semiconductor laser according to still another embodiment of the present invention.

FIG. 8 is a sectional view showing a device structure of a gallium nitride-based compound semiconductor laser according to still another embodiment of the present invention.

FIG. 9 is a sectional view showing an element structure of a gallium nitride-based compound semiconductor laser according to still another embodiment of the present invention.

FIG. 10 is a sectional view showing an element structure of a gallium nitride-based compound semiconductor laser according to still another embodiment of the present invention.

FIG. 11 is a sectional view showing an element structure of a gallium nitride-based compound semiconductor laser according to still another embodiment of the present invention.

FIG. 12 is a view showing an impurity concentration profile near a current block layer of the semiconductor laser shown in FIG. 11;

FIG. 13 is a cross-sectional view showing a device structure of a gallium nitride-based compound semiconductor laser according to still another embodiment of the present invention.

FIG. 14 is a sectional view showing a device structure of a gallium nitride-based compound semiconductor laser according to still another embodiment of the present invention.

FIG. 15 is a sectional view showing a device structure of a gallium nitride-based compound semiconductor laser according to still another embodiment of the present invention.

FIG. 16 is a sectional view showing a device structure of a gallium nitride-based compound semiconductor laser according to still another embodiment of the present invention.

FIG. 17 is a sectional view showing a device structure of a gallium nitride-based compound semiconductor laser according to still another embodiment of the present invention.

FIG. 18 is a sectional view showing a device structure of a gallium nitride-based compound semiconductor laser according to still another embodiment of the present invention.

FIG. 19 is a sectional view showing an element structure of a gallium nitride-based compound semiconductor laser according to still another embodiment of the present invention.

FIG. 20 is a sectional view showing a device structure of a gallium nitride-based compound semiconductor laser according to still another embodiment of the present invention.

21 (a) to (c) are cross-sectional views showing a first half of a method of manufacturing the semiconductor laser shown in FIG. 20.

FIGS. 22A to 22C are cross-sectional views showing the latter half of the method of manufacturing the semiconductor laser shown in FIG. 20;

FIG. 23 is a scanning electron micrograph showing the periphery of the opening after the p-contact layer is regrown in the semiconductor laser shown in FIG. 20;

FIG. 24 is an enlarged sectional view showing the periphery of an opening of the semiconductor laser shown in FIG. 20;

FIGS. 25A to 25C are cross-sectional views showing the first half of a method for manufacturing a gallium nitride-based compound semiconductor laser according to still another embodiment of the present invention.

FIGS. 26A to 26C are cross-sectional views illustrating the latter half of the method of manufacturing the semiconductor laser, following FIGS. 25A to 25C;

FIGS. 27A to 27C are cross-sectional views showing the first half of a method for manufacturing a gallium nitride-based compound semiconductor laser according to still another embodiment of the present invention.

28A is an enlarged cross-sectional view showing the periphery of the opening after the p-contact layer is regrown in the semiconductor laser shown in FIGS. 27A to 27C, and FIG. 6 is a graph showing the relationship between the width of the upper part of the graph and the depth of the groove on the surface of the p-contact layer, with the depth of the opening as a variable.

FIG. 29 is a cross-sectional view showing a device structure of a gallium nitride-based compound semiconductor laser according to still another embodiment of the present invention.

30 (a) to (c) are cross-sectional views showing a method for manufacturing the semiconductor laser shown in FIG. 29.

FIG. 31 is a cross-sectional view showing a device structure of a gallium nitride-based compound semiconductor laser according to still another embodiment of the present invention.

32 (a) to (c) are cross-sectional views showing a method for manufacturing the semiconductor laser shown in FIG. 31.

FIG. 33 is a sectional view showing a device structure of a gallium nitride-based compound semiconductor laser according to still another embodiment of the present invention.

34 (a) to (c) are cross-sectional views showing a method for manufacturing the semiconductor laser shown in FIG. 33.

FIG. 35 is a scanning electron microscope photograph showing the periphery of the opening after the growth of the p-contact layer and the formation of the electrodes in the semiconductor laser shown in FIG. 33;

FIG. 36 is a sectional view showing an element structure of a gallium nitride-based compound semiconductor laser according to still another embodiment of the present invention.

FIG. 37 is a sectional view showing an element structure of a gallium nitride-based compound semiconductor laser according to still another embodiment of the present invention.

FIG. 38 is a sectional view showing a device structure of a gallium nitride-based compound semiconductor laser according to still another embodiment of the present invention.

FIG. 39 is a sectional view showing a device structure of a gallium nitride-based compound semiconductor laser according to still another embodiment of the present invention.

FIG. 40 is a sectional view showing an element structure of a gallium nitride-based compound semiconductor laser according to still another embodiment of the present invention.

FIG. 41 is a sectional view showing an element structure of a gallium nitride-based compound semiconductor laser according to still another embodiment of the present invention.

FIG. 42 is a sectional view showing a device structure of a gallium nitride-based compound semiconductor laser according to still another embodiment of the present invention.

FIG. 43 is a cross-sectional view showing a device structure of a gallium nitride-based compound semiconductor laser according to still another embodiment of the present invention.

FIG. 44 is a sectional view showing an element structure of a gallium nitride-based compound semiconductor laser according to still another embodiment of the present invention.

FIG. 45 is a sectional view showing a device structure of a gallium nitride-based compound semiconductor laser according to still another embodiment of the present invention.

FIG. 46 is a sectional view showing an element structure of a gallium arsenide-based compound semiconductor laser according to still another embodiment of the present invention.

FIG. 47 is a cross-sectional view showing a device structure of a gallium nitride-based compound semiconductor laser according to still another embodiment of the present invention.

FIG. 48 is a cross-sectional view showing a device structure of a gallium nitride-based compound semiconductor laser according to still another embodiment of the present invention.

FIG. 49 is a sectional view showing a device structure of a gallium nitride-based compound semiconductor laser according to still another embodiment of the present invention.

FIG. 50 is a sectional view showing an element structure of a gallium nitride-based compound semiconductor light-receiving element according to still another embodiment of the present invention.

DESCRIPTION OF SYMBOLS 10 ... Sapphire substrate 11 ... Non-doped GaN buffer layer 12 ... n-GaN contact layer 13 ... n-GaAlN cladding layer 14 ... MQW active layer 15 ... p-GaAlN cladding layer 16 ... GaN current block layer 17 ... p -GaN buried layer 18-p-GaN contact layer 21-n-side electrode 22-p-side electrode 31, 51, 52-InGaN surface protection layer 35-backside metal film 36-heat sink 37-fusion metal 55-passivation film 62 64 AlN current block layer 66 periodic structure 72 etching stop layer 74 SiO ₂ layer 76 resist layer 77 opening 82 82 Ti or Al layer 84 resist layer 90 SiC substrate 92 p-GaN contact layer (Current injection layer) 93, 94, 106, 116, 132, 137, 1 2
... Current blocking layer 136, 146 ... Electrode extraction layer

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Joji Nishio 1st address, Toshiba R & D Center, Komukai Toshiba-cho, Kawasaki-shi, Kanagawa Prefecture (72) Inventor Hidetoshi Fujimoto 1st location of Komukai Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Pref.

Claims (21)

[Claims] 1. An active layer having a periodic structure composed of a repetition of two or more types of semiconductor layers, and a first layer and a first layer, which are disposed with the active layer interposed therebetween so as to form a double heterojunction structure. First and second cladding layers of two conductivity type, and first and second cladding layers connected to the first and second cladding layers.
An electrode, disposed between the second electrode and the second cladding layer,
A current block layer having a stripe-shaped opening for confining current to the double heterojunction structure; a current block layer disposed between the second electrode and the current block layer and in the opening; Each of the current injection layer having a large area, the active layer, the first and second cladding layers, the current block layer, and the current injection layer is basically made of a material represented by the following composition formula. _{, in x Ga y Al z N} , wherein x + y + z = 1,0 ≦
x, y, z ≦ 1 When the thickness of the current blocking layer is TA and the distance between the current blocking layer and the active layer is TB, TB <TA
Gallium nitride based compound semiconductor laser characterized by satisfying the following conditions: 2. The gallium nitride-based compound semiconductor laser according to claim 1, wherein a condition of 2TB <TA is satisfied. 3. The gallium nitride based compound semiconductor laser according to claim 2, wherein a condition of 2 TB <TA <10 TB is satisfied. 4. The gallium nitride-based compound semiconductor laser according to claim 1, wherein when the thickness of the current injection layer excluding the inside of the opening is TC, the condition TC <TA is satisfied. 5. The gallium nitride-based compound semiconductor laser according to claim 1, wherein a condition of TB <TC is satisfied, where TC is a thickness of the current injection layer excluding the inside of the opening. 6. The method according to claim 1, wherein the current blocking layer comprises a doped second layer.
The gallium nitride-based compound semiconductor laser according to claim 1, further comprising a conductive impurity. 7. The gallium nitride-based system according to claim 1, wherein a side wall of the opening and an interface between the current blocking layer and the current injection layer form an angle of 45 ° to 90 °. Compound semiconductor laser. 8. An active layer having a periodic structure composed of a repetition of two or more types of semiconductor layers, and a first and a second layer, respectively, which are disposed with the active layer interposed therebetween so as to form a double hetero junction structure. First and second cladding layers of two conductivity type, and first and second cladding layers connected to the first and second cladding layers.
An electrode, disposed between the second electrode and the second cladding layer,
A current block layer having a stripe-shaped opening for confining current to the double heterojunction structure; a current block layer disposed between the second electrode and the current block layer and in the opening; Each of the current injection layer having a large area, the active layer, the first and second cladding layers, the current block layer, and the current injection layer is basically made of a material represented by the following composition formula. _{, in x Ga y Al z N} , wherein x + y + z = 1,0 ≦
x, y, z ≦ 1 When the thickness of the current blocking layer is TA and the thickness of the current injection layer excluding the inside of the opening is TC, the condition of TC <TA is satisfied. A gallium nitride-based compound semiconductor laser characterized by the following. 9. A stripe-shaped V-shaped groove is formed on the surface of the current injection layer above the opening, and the second electrode has a portion in the groove that contacts the current injection layer. The gallium nitride-based compound semiconductor laser according to claim 8, wherein: 10. When the depth of the opening is d1 and the widths of the upper and lower portions of the opening are W1 and W2, respectively, 24
The gallium nitride-based compound semiconductor laser according to claim 9, wherein a condition of <(W1 + W2) * d1 / TC is satisfied. 11. An active layer having a periodic structure composed of a repetition of two or more types of semiconductor layers, and a first layer and a first layer disposed to sandwich the active layer so as to form a double heterojunction structure. First and second cladding layers of two conductivity type, and first and second cladding layers connected to the first and second cladding layers.
An electrode, disposed between the second electrode and the second cladding layer,
A current block layer having a stripe-shaped opening for confining current to the double hetero junction structure; and a current block layer disposed between the second electrode and the current block layer;
Each of the current injection layer having an area larger than the opening, the active layer, the first and second cladding layers, the current block layer, and the current injection layer is made of a material represented by the following composition formula. and it is the _{target, in x Ga y Al z N} , wherein x + y + z = 1,0 ≦
x, y, z ≦ 1 The distance between the current blocking layer and the active layer is represented by TB,
A gallium nitride based compound semiconductor laser characterized by satisfying a condition of TB <TC, where TC is the thickness of the current injection layer excluding the inside of the opening. 12. An active layer having a periodic structure composed of a repetition of two or more types of semiconductor layers, and a first and a second layer, respectively, which are disposed with the active layer interposed therebetween so as to form a double hetero junction structure. First and second cladding layers of two conductivity type, and first and second cladding layers connected to the first and second cladding layers.
An electrode, disposed between the second electrode and the second cladding layer,
A current block layer having a stripe-shaped opening for confining current to the double heterojunction structure; a current block layer disposed between the second electrode and the current block layer and in the opening; Each of the current injection layer having a large area, the active layer, the first and second cladding layers, the current block layer, and the current injection layer is basically made of a material represented by the following composition formula. _{, in x Ga y Al z N} , wherein x + y + z = 1,0 ≦
x, y, z ≦ 1 The portion of the current injection layer adjacent to the active layer has a band gap larger than a band gap corresponding to an emission wavelength of the active layer and has a larger refractive index than the current blocking layer. And a gallium nitride-based compound semiconductor laser. 13. The gallium nitride compound semiconductor laser according to claim 12, wherein said second cladding layer and said current blocking layer have substantially the same refractive index. 14. The gallium nitride-based compound semiconductor laser according to claim 12, wherein a portion of said current injection layer adjacent to said active layer and said second cladding layer have substantially the same refractive index. 15. An active layer having a periodic structure formed by repeating two or more types of semiconductor layers, and first and second active layers disposed to sandwich the active layer to form a double heterojunction structure. First and second cladding layers of two conductivity type, and first and second cladding layers connected to the first and second cladding layers.
An electrode, disposed between the second electrode and the second cladding layer,
A current block layer having a stripe-shaped opening for confining current to the double heterojunction structure; a current block layer disposed between the second electrode and the current block layer and in the opening; Each of the current injection layer having a large area, the active layer, the first and second cladding layers, the current block layer, and the current injection layer is basically made of a material represented by the following composition formula. _{, in x Ga y Al z N} , wherein x + y + z = 1,0 ≦
x, y, z ≦ 1 The current blocking layer has a band gap larger than a band gap corresponding to an emission wavelength of the active layer, and has a larger refractive index than a portion of the current injection layer adjacent to the active layer. And a gallium nitride-based compound semiconductor laser. 16. An active layer having a periodic structure composed of a repetition of two or more types of semiconductor layers, and a first and a second, respectively, disposed with the active layer interposed therebetween so as to form a double hetero junction structure. First and second cladding layers of two conductivity type, and first and second cladding layers connected to the first and second cladding layers.
An electrode, disposed between the second electrode and the second cladding layer,
A current block layer having a stripe-shaped opening for confining current to the double heterojunction structure; a current block layer disposed between the second electrode and the current block layer and in the opening; Each of the current injection layer having a large area, the active layer, the first and second cladding layers, the current block layer, and the current injection layer is basically made of a material represented by the following composition formula. _{, in x Ga y Al z N} , wherein x + y + z = 1,0 ≦
x, y, z ≦ 1 A portion of the current injection layer adjacent to the active layer has a band gap larger than a band gap corresponding to an emission wavelength of the active layer, and the current blocking layer includes:
Having a band gap smaller than a band gap corresponding to an emission wavelength of the active layer. 17. An active layer having a periodic structure composed of a repetition of two or more types of semiconductor layers, and a first layer and a first layer, which are disposed with the active layer interposed therebetween so as to form a double hetero junction structure. First and second cladding layers of two conductivity type, and first and second cladding layers connected to the first and second cladding layers.
An electrode, disposed between the second electrode and the second cladding layer,
A current block layer having a stripe-shaped opening for confining current to the double heterojunction structure; a current block layer disposed between the second electrode and the current block layer and in the opening; Each of the current injection layer having a large area, the active layer, the first and second cladding layers, the current block layer, and the current injection layer is basically made of a material represented by the following composition formula. _{, in x Ga y Al z N} , wherein x + y + z = 1,0 ≦
x, y, z ≦ 1 A stripe-shaped groove continuous with the opening is formed on the surface of the second cladding layer, and the current injection layer is disposed in the groove so as to be in contact with the second cladding layer. A gallium nitride based compound semiconductor laser. 18. An active layer, first and second conductive-type first and second cladding layers disposed to sandwich the active layer so as to form a double heterojunction structure, respectively, And the first and second connected to the second cladding layer.
An electrode, disposed between the second electrode and the second cladding layer,
A current block layer having a stripe-shaped opening for confining current to the double heterojunction structure; a current block layer disposed between the second electrode and the current block layer and in the opening; Each of the current injection layer having a large area, the active layer, the first and second cladding layers, the current block layer, and the current injection layer is basically made of a material represented by the following composition formula. _{, in x Ga y Al z N} , wherein x + y + z = 1,0 ≦
A method for manufacturing a gallium nitride-based compound semiconductor laser having x, y, z ≦ 1, wherein a step of forming a laminated film having the double heterostructure on a support substrate; Laminating a surface protection layer and a surface protection layer; etching a part of the surface protection layer and the current block layer to form the stripe-shaped opening; leaving the surface protection layer at a high temperature in a gas phase Forming the current injection layer in the opening and on the current block layer after the crystal is removed by re-evaporation of the gallium nitride-based compound semiconductor laser. 19. An active layer, first and second conductive-type first and second cladding layers disposed to sandwich the active layer so as to form a double heterojunction structure. And the first and second connected to the second cladding layer.
An electrode, disposed between the second electrode and the second cladding layer,
A current block layer having a stripe-shaped opening for confining current to the double heterojunction structure; a current block layer disposed between the second electrode and the current block layer and in the opening; Each of the current injection layer having a large area, the active layer, the first and second cladding layers, the current block layer, and the current injection layer is basically made of a material represented by the following composition formula. _{, in x Ga y Al z N} , wherein x + y + z = 1,0 ≦
A method of manufacturing a gallium nitride-based compound semiconductor laser having x, y, z ≦ 1, comprising: forming a laminated film having the double hetero structure on a supporting substrate; and forming the current blocking layer on the laminated film. Forming a stripe-shaped opening by dry-etching a part of the current block layer; heating the support substrate, the laminated film, and the current block layer to 100 ° C. or more. Forming a current injection layer in the opening and on the current block layer after immersion in a solution of HNO ₃ : HCl = 3: 1, wherein the gallium nitride-based compound semiconductor laser is provided. Manufacturing method. 20. An active layer, first and second conductive-type first and second cladding layers disposed to sandwich the active layer so as to form a double heterojunction structure. And the first and second connected to the second cladding layer.
An electrode, disposed between the second electrode and the second cladding layer,
A current block layer having a stripe-shaped opening for confining current to the double heterojunction structure; a current block layer disposed between the second electrode and the current block layer and in the opening; Each of the current injection layer having a large area, the active layer, the first and second cladding layers, the current block layer, and the current injection layer is basically made of a material represented by the following composition formula. _{, in x Ga y Al z N} , wherein x + y + z = 1,0 ≦
A method for manufacturing a gallium nitride-based compound semiconductor laser having x, y, z ≦ 1, wherein a step of forming a laminated film having the double hetero structure on a supporting substrate; Forming a current blocking layer having the stripe-shaped openings by partially introducing impurities into a selected layer formed of one or both of the second cladding layer and the current injection layer. A method for manufacturing a gallium nitride-based compound semiconductor laser. 21. The method according to claim 20, wherein the selected layer contains one or both of Mg and Al, and the impurity is O.