JPH0697576A - Semiconductor laser and manufacturing method thereof - Google Patents

Abstract

(57) [Abstract] [Purpose] To obtain a multi-beam laser capable of lower threshold and stable independent drive. A first conductivity type first cladding layer is formed on a ridge 2 formed along a <011> crystal axis direction on a first conductivity type compound semiconductor substrate 1 having a {100} crystal plane as a main surface. 3 and the current blocking layer 4 have an epitaxial growth layer of {11
1} B cross section sandwiched between B crystal planes
A prismatic semiconductor portion E is formed and divided by the semiconductor portion E, and at least both sides of the semiconductor portion E have a second clad layer 5 of a first conductivity type, an active layer 6, and a third clad layer of a second conductivity type. 7, first-conductivity-type current confinement layer 8 and second-conductivity-type fourth cladding layer 9, respectively, to form first and second semiconductor laser sections LD ₁ and LD ₂ .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser, particularly to A
The present invention relates to a semiconductor laser which is made of a 1 GaAs-based compound semiconductor and has an independently driven type, for example, a two-beam semiconductor laser as a basic structure, and a manufacturing method thereof.

[0002]

2. Description of the Related Art A multi-beam semiconductor laser having a plurality of independently controllable laser beams in one chip has been developed in response to a demand for higher integration and faster processing of semiconductor lasers.

Since such an independently controlled multi-beam laser requires a plurality of independent input terminals, unlike a single element, for example, an independent electrode is patterned for each laser beam and further traverses the active layer. A method is conceivable in which trenches are formed to a depth to reach the depth by dry etching such as RIE (reactive ion etching) to separate elements.

However, when dry etching is performed across the active layer in this manner, there is a risk that the crystal may be damaged, the characteristics may be deteriorated, and the reliability may be deteriorated.

The applicant of the present invention has previously described a SAN laser (Self Aligned Narr) which is a high-power semiconductor laser.
A two-beam laser was proposed as a multi-beam laser for the ow Stripe Laser.

As shown in the sectional view of FIG. 6, this two-beam SAN laser is first formed on a GaAs compound semiconductor substrate 31 of the first conductivity type, for example, n type, and one main surface of which has a {100} crystal plane, for example, MOCVD. (Organometallic chemical vapor deposition)
First conductivity type, for example, an n-type first cladding layer 32, an undoped active layer 33, a second conductivity type, for example, a p-type second cladding layer 34, and a first conductivity type current block. A wafer is obtained in which the layer 35 is epitaxially grown.

Then, the growth is once stopped, the wafer is taken out from the growth apparatus, and then a groove 44 is formed in a portion which will be a current path of a laser element finally obtained by etching.
Then, the wafer is put into the growth apparatus again, and the second conductivity type third cladding layer 36 is formed by the second crystal growth.
Then, the second conductivity type cap layer 37 is epitaxially grown.

Thereafter, in order to separate the elements, R
The groove 45 is formed by dry etching such as IE.

Then, electrodes 46 and 47 are independently ohmic-deposited on the cap layer 37 separated by the groove 45, and a common electrode 48 is ohmic-deposited on the back surface of the compound semiconductor substrate 31.

However, in the method of manufacturing the two-beam SAN laser, the crystal of the active layer 33 is damaged when dry etching is performed to form the groove 45 traversing the active layer 33, and the groove 45 is formed with good control. Difficult, 2 independent from each other across this etching process
Since the crystal growth is performed twice, the reliability is lowered.

[0011]

SUMMARY OF THE INVENTION The present invention provides a semiconductor laser having an independently driven two-beam laser basic structure with improved controllability and reliability, and a method of manufacturing the same.

[0012]

The present invention is based on FIG. 1 and FIG.
As shown in the cross-sectional views of the respective examples, <011> is formed on the compound semiconductor substrate 1 of the first conductivity type having the {100} crystal plane as the main surface.
The ridge 2 formed along the crystal axis direction, the first clad layer 3 of the first conductivity type, and the current blocking layer 4 formed on the ridge 2 are epitaxially grown layers having a slope S _{1 of a} {111} B crystal plane. And a semiconductor portion E having a substantially triangular cross section sandwiched by S ₂ and confined, and a second cladding layer 5 of at least a first conductivity type and an active layer 6 on both sides thereof divided by the semiconductor portion E. , A second conductive type third clad layer 7, a first conductive type current confinement layer 8 and a second conductive type fourth clad layer 9, respectively. ₁ and LD ₂ are configured.

Further, in the present invention, in the above structure, the light emitting region of each active layer 6 of the first and second semiconductor laser sections LD ₁ and LD ₂ has {311} B as a main surface.

The manufacturing method of the present invention has the following structure.
The step of forming the ridge 2 along the <011> crystal axis direction on the first conductivity type compound semiconductor substrate 1 having the {100} crystal plane as the main surface, and the step of forming the ridge 2 and the groove portions 11 on both sides thereof at least in the first direction. First conductivity type first cladding layer 3, current blocking layer 4, first conductivity type second cladding layer 5, and active layer 6
And a step of epitaxially growing a second conductivity type third clad layer 7, a first conductivity type current confinement layer 8 and a second conductivity type fourth clad layer 9 on the ridge 2. In addition, the epitaxially grown layer of the first conductivity type first cladding layer 3 and the current blocking layer 4 is confined by the {111} B crystal plane between the slopes S ₁ and S ₂ and confined to a cross section of approximately 3
In addition to forming the prismatic semiconductor portion E, the semiconductor portion E is divided by the semiconductor portion E, and at least both sides of the semiconductor portion E are the second clad layer 5 of the first conductivity type, the active layer 6, and the third clad of the second conductivity type. A semiconductor laser including first and second semiconductor laser portions LD ₁ and LD ₂ each having a layer, a first conductivity type current confinement layer 8 and a second conductivity type fourth clad layer 9. obtain.

[0015]

As described above, in the present invention, {100}
The ridge 2 is provided in the <011> crystal axis direction on the compound semiconductor substrate 1 on the crystal plane, only the first cladding layer 3 and the current blocking layer 4 are formed on the ridge 2, and the active layer 6 sandwiches the ridge 2. And make it independent on both sides.

In this structure, the epitaxial growth layer grown from above the groove portion 11 so as to abut on both side slopes S ₁ and S ₂ of the semiconductor portion E on the ridge 2 has a {311} B crystal near the semiconductor portion E. It will grow as a face.

Since the {311} B plane has a small incorporation of carbon, that is, p-type dopant, n
Utilizing the property of being easily formed into a mold, for example, as described later, by controlling the carrier concentration of the cap layer 10 formed on the fourth cladding layer 9, the opening a of the current blocking layer 8 is formed. Can be controlled automatically.
In other words, the current blocking layer 8 can narrow the injection current path to the active layer, thereby lowering the threshold value, and thereby the semiconductor laser section LD.
_It is possible to drive ₁ and LD ₂ independently.

Further, according to the manufacturing method of the present invention, the active layer 6 separated by the ridge 2 is formed in the triangular columnar semiconductor portion E by the first cladding layer 3 and the current blocking layer 4 grown on the ridge 2. Slopes S ₁ and S _{2 formed} by the {111} B plane, that is, semiconductor lasers LD ₁ and LD on both sides of the semiconductor portion E.
The end face of the active layer 6 constituting ₂ is formed with good crystallinity.

Further, according to the manufacturing method of the present invention, an arbitrary number of beams can be formed by forming a plurality of ridges 2 and performing element isolation by each ridge 2.

Further, according to the method of the present invention, since each semiconductor layer can be formed by one continuous epitaxial growth, a highly reliable semiconductor laser can be constructed.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of the independently driven two-beam semiconductor laser according to the present invention shown in FIG. 1 will be described in detail with reference to FIG. 3 together with an example of the manufacturing method according to the present invention. In this example, a case where a two-beam laser made of AlGaAs compound semiconductor is obtained is shown.

First, as shown in FIG. 3A, a resist RS is formed in stripes along the <011> crystal axis direction on the main surface 1S made of the {100} crystal plane of the compound semiconductor substrate 1 made of p-type GaAs or the like. Adhering and forming.

As shown in FIG. 3B, a striped ridge 2 is formed in the direction <011> perpendicular to the plane of the drawing by wet etching, dry etching, or the like except for the portion where the resist RS is adhered.

Next, as shown in FIG. 3C, the same conductivity type as that of the substrate 1, that is, p-type AlG, is obtained by epitaxial growth by MOCVD using a methyl-based source gas.
The first cladding layer 3 of aAs is grown.

Subsequently, as shown in FIG. 3D, for example, p-type AlGaA having the same conductivity type as the first cladding layer 3 and the conductivity type opposite to that of the first cladding layer 3.
A current blocking layer 4 having a thyristor structure is grown by repeating s, n-type AlGaAs, ....

At this time, {111} B crystal planes are formed on the ridge 2 from both side edges thereof.
When the 1} B crystal plane is generated, the epitaxial growth rate is extremely slow on the 1} B crystal plane. Therefore, the triangular columnar semiconductor portion surrounded by the slopes S ₁ and S ₂ of the {111} B crystal plane is formed on the ridge 2. E is constructed.

Subsequently, that is, by continuous epitaxy, the second cladding layer 5 is, for example, a p-type AlGaAs layer as shown in FIG. 4A, and, for example, GaA as shown in FIG. 4B.
s or active layer 6 made of InGaAs, for example n-type A
A third clad layer 7 made of 1GaAs and a current blocking layer 8 made of p-type AlGaAs, for example, are sequentially epitaxially grown as shown in FIG. 4C, and then a fourth clad layer 9 made of n-type AlGaAs, for example, is grown as shown in FIG. Then, as shown in FIG. 5B, the n-type GaAs cap layer 10 is grown.

At this time, since the ridge 2 is covered with the {111} B planes S ₁ and S ₂ , the epitaxial growth layer after the current blocking layer 4 of the thyristor region structure is the ridge 2.
It is formed on both sides of the upper semiconductor portion E with the semiconductor portion E interposed therebetween.

During the growth of the cap layer 10, the {311} B plane of the current confinement layer 8 is n-typed by the carrier concentration of the cap layer 10, and the carrier concentration of the current confinement layer 8 and the cap layer An opening a is formed in which the current is blocked, the width of which is determined by the carrier concentration of 10 and the like. The width of the opening a is wide when the air concentration of the cap layer is high and narrow when the air concentration is low.

In this way, the two lasers LD ₁ and LD ₂ , that is, the two-beam laser, having the current confinement layer 8 having the opening a as a current path on both sides of the ridge 2 are easily formed.

Then, as shown in FIG. 5C and FIG. 1, independent first and second electrodes 31 and 32 on both sides of the semiconductor portion E are ohmic-deposited on the respective caps, and the back surface of the substrate 1 is covered. The common third electrode 33 is ohmically deposited.

In this structure, when the impurity concentration of the current confinement layer 8 is set to about 1 × 10 ¹⁸ atoms / cm ³ and the third and fourth cladding layers 7 and 9 are set to about 1 × 10 ¹⁸ atoms / cm ³ , The width of the opening a serving as a current path is 1 μm, and the concentration is 5 × 1.
It could be set to 0 ¹⁷ atoms / cm ³ .

The present invention is not limited to the above-mentioned embodiment, but the conductivity type of each part in FIG. 1 is reverse conductivity type as shown in FIG. 2, for example. However, when the conductivity type is reversed, the GaAs buffer layer 34 is formed on the current blocking layer 4 on both sides of the ridge 2 and the current blocking layer 8 is formed below the active layer 6. Then, in this case, the opening portion a is similarly formed in the current blocking layer 8 by the carrier concentration of the GaAs buffer layer 34 to perform the current constriction.

In FIG. 2, parts corresponding to those in FIG. 1 are designated by the same reference numerals, and duplicated description will be omitted.

Needless to say, various modifications and changes are possible without being limited to the above-mentioned examples.

[0036]

As described above, according to the present invention, a semiconductor laser having high reliability can be constructed with good workability because it can be manufactured by one continuous epitaxial growth without requiring etching.

In addition to this, for example, by controlling the carrier concentration of the cap layer or the buffer layer, the opening a serving as a current path is set, in other words, the current is narrowed, so that stable and uniform characteristics can be obtained. Independently driven two-beam lasers can be realized.

[Brief description of drawings]

FIG. 1 is a schematic enlarged cross-sectional view of an example of a semiconductor laser according to the present invention.

FIG. 2 is a manufacturing process diagram of an example of a method of manufacturing an independently driven two-beam laser according to the present invention.

FIG. 3 is a partial process chart (1) of an example of the method of the present invention.

FIG. 4 is a partial process chart (2) of the example of the method of the present invention.

FIG. 5 is a partial process chart (3) of the example of the method of the present invention.

FIG. 6 is a schematic enlarged cross-sectional view of an example of a conventional two-beam laser.

[Explanation of symbols]

 1 Compound Semiconductor Substrate 2 Ridge 3 First Cladding Layer 5 Second Cladding Layer 7 Third Cladding Layer 9 Fourth Cladding Layer 6 Active Layer

Claims (3)

[Claims] 1. A ridge formed along a <011> crystal axis direction on a compound semiconductor substrate of the first conductivity type having a {100} crystal plane as a main surface, and a first conductivity type first ridge formed on the ridge. No. 1 clad layer and a current blocking layer, an epitaxial growth layer is sandwiched by {111} B crystal planes and confined, and a semiconductor portion having a substantially triangular cross section, and the semiconductor portion is divided by at least the first portion. It has a conductive type second clad layer, an active layer, a second conductive type third clad layer, a first conductive type current confinement layer, and a second conductive type fourth clad layer. A semiconductor laser comprising first and second semiconductor laser sections. 2. A semiconductor laser, wherein the light emitting regions of the respective active layers of the first and second semiconductor laser sections have {311} B as a main surface. 3. A step of forming a ridge along a <011> crystal axis direction on a first-conductivity-type compound semiconductor substrate having a {100} crystal plane as a main surface, and at least in the ridge and groove portions on both sides thereof. A first clad layer of a first conductivity type, a second clad layer of a first conductivity type, an active layer, a third clad layer of a second conductivity type, a first clad layer
A step of epitaxially growing a conductivity type current confinement layer and a second conductivity type fourth clad layer is used to form a first conductivity type first clad layer and a current blocking layer on the ridge. The epitaxial growth layer forms a semiconductor portion having a substantially triangular cross section sandwiched and confined by {111} B crystal planes, and the semiconductor portion is divided by the semiconductor portion and has at least a second clad layer of the first conductivity type on both sides thereof. First and second semiconductor lasers each having an active layer, a second conductivity type third cladding layer, a first conductivity type current confinement layer, and a second conductivity type fourth cladding layer. A method of manufacturing a semiconductor laser, characterized in that a semiconductor laser having a section is obtained.