JPH10209559A - Semiconductor light emitting device and method of manufacturing the same - Google Patents

Abstract

[PROBLEMS] To realize a highly reliable semiconductor light emitting device having an improved adhesion between a contact layer and a p-type electrode. SOLUTION: An n-type GaAs is formed on an n-type GaAs substrate 111.
s buffer layer 112, n-type ZnMgSSe cladding layer 1
13, n-type ZnSSe optical waveguide layer 114, ZnCdSe active layer 115, p-type ZnSSe optical waveguide layer 116, p-type Zn
An MgSSe clad layer 117 and a p-type ZnSeTe contact layer 118 are stacked. A p-type electrode 120 is formed on the contact layer 118, and a ZnO insulating layer 119 is formed on both sides thereof. Here, the p-type AuSe electrode 120 is formed in a region on the p-type ZnSeTe contact layer 118 before the formation of the ZnO insulating layer 119, and heat treatment is performed, so that the p-type ZnSeTe contact layer 118 and the p-type AuPd electrode 120 are alloyed. As a result, an electrode having high adhesion and ohmic contact with the stripe region can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light emitting device used for optical communication, optical information processing and the like.

[0002]

2. Description of the Related Art In recent years, demands for semiconductor light emitting devices have increased in fields such as optical communication and optical information processing.
Since a group VI compound semiconductor is a direct transition type and has a wide band gap, research and development of a blue-green semiconductor laser using the same are actively performed. As a conventional example, ZnSe
The structure of a blue-green semiconductor laser using a system II-VI compound semiconductor and a p-type electrode forming step will be described. FIG. 9 shows the structure of the blue-green semiconductor laser.

[0003] 201 is an n-type GaAs substrate doped with Si, 202 is an n-type GaAs buffer layer doped with Si, 203 is an n-type ZnMgSSe cladding layer doped with Cl, and 204 is an n-type ZnSSe optical waveguide layer doped with Cl. , 205 is a ZnCdSe active layer, 206 is an N-doped p-type ZnSSe optical waveguide layer, 207 is an N-doped p-type ZnMgSSe cladding layer, 208 is an N-doped p-type ZnSeTe contact layer, 209 is a ZnO insulating layer, 210 is a p-type AuPd electrode, 211 is AuGeN
An n-type electrode made of i. These semiconductor multilayer films are formed by a molecular beam epitaxy method. Next, as a p-type electrode forming step, the p-type ZnTe contact layer 208 and the p-type Z
A part of the nMgSSe cladding layer 207 is etched leaving a stripe region. A ZnO insulating film 209 is deposited on the etched portion of the p-type ZnMgSSe clad layer 207, and a PdAu electrode 210 is deposited on the entire surface by using a substrate heating method.
A heat treatment at about ° C is performed.

[0004]

However, unlike the conventional III-V semiconductor, the II-VI semiconductor crystal used in the semiconductor laser has a growth temperature of 300.degree.
Therefore, various problems are likely to occur in the above process.

In the case of forming a p-type electrode of a II-VI compound semiconductor laser, as a general forming method, an insulating film 209 is formed on the semiconductor epitaxial layer 207 in a region other than a stripe region, and a p-type electrode 210 is deposited by an Heat treatment is performed to obtain sexual contact. At this time, the ZnO insulating film 2
Separation due to a difference in thermal expansion coefficient between the interface 09 and the semiconductor epitaxial layer 207 is likely to occur. Further, since electrode materials such as PdAu have weak adhesion to an insulating film such as ZnO,
Separation easily occurs between the nO insulating film 209 and the p-type electrode 210.

Generally, as a method of increasing the adhesion between the insulating film 209 and the p-type electrode 210, it is conceivable to raise the substrate temperature to 200 ° C. or higher. However, ZnSe II-
The crystal growth temperature of a group VI compound semiconductor laser is generally 20
Since the temperature is as low as 0 ° C. to 300 ° C., deterioration of crystal quality is caused by heating the substrate. Therefore, the temperature at the time of electrode formation must be set lower than that, and the effect of increasing the adhesion cannot be expected.

Further, the semiconductor epitaxial layer 207 and Z
It is difficult to completely suppress peeling due to a difference in thermal expansion coefficient between the uO insulating layers 209 as long as a heat treatment step exists. If the electrodes and the insulating film are not in close contact with each other, the current injection becomes non-uniform, and the heat radiation after the mounting of the device is liable to occur, thereby deteriorating the device characteristics.

The present invention has been made in view of the above problems, and provides a p-type ohmic electrode structure excellent in adhesion of a II-VI compound semiconductor light emitting device and a method of manufacturing the same. .

[0009]

Means for solving the problem are as follows.

(1) An active region formed of a II-VI compound semiconductor, a contact layer formed on the active region, and a first stripe-shaped electrode for obtaining ohmic contact with the contact layer And an insulating film deposited on a side region of the stripe electrode, and a second p-type electrode formed on the first electrode and the insulating film in a stripe shape and having high adhesion to the first electrode. And a semiconductor light emitting element having the following.

(2) An active region formed of a II-VI compound semiconductor, a contact layer formed on the active region, and a first stripe-shaped electrode for obtaining ohmic contact with the contact layer An electrode containing Ni on the stripe electrode; an insulating film deposited on a side region of the stripe electrode; and a second electrode formed on the Ni electrode and the insulating film and having high adhesion to the Ni electrode. And a semiconductor light emitting device having the p-type electrode.

(3) a step of performing dry etching using chlorine gas; a heat treatment step for obtaining ohmic contact after the dry etching step; a step of depositing an insulating film after the heat treatment step; And a step of forming a second electrode.

(4) A striped Ni electrode is formed on a striped p-type AuPd first electrode for obtaining ohmic contact on the II-VI compound semiconductor epitaxial layer, and dry etching is performed using the striped Ni electrode as a mask. By forming a smooth current confinement structure, light confinement is improved, and a semiconductor light emitting device having single transverse mode laser characteristics is obtained.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) FIG. 1 is a structural sectional view of a blue-green semiconductor laser using a ZnSe-based II-VI group semiconductor.

Reference numeral 111 denotes an n-type GaAs substrate doped with Si, 112 denotes an n-type GaAs buffer layer doped with Si, 113 denotes an n-type ZnMgSSe clad layer doped with Cl, and 114 denotes an n-type ZnSSe optical waveguide layer doped with Cl. 115, a ZnCdSe active layer, 116, an N-doped p-type ZnSSe optical waveguide layer, 117, an N-doped p-type ZnMgSSe cladding layer, 118, a p + type Zn
SeTe contact layer, 119 is ZnO insulating layer, 120
Is a p-type first electrode composed of two layers of Au and Pd, and 121 is N
A p-type second electrode composed of two layers of an i-electrode 122 and an Au electrode 123 is an n-type electrode made of AuGeNi.

In the present embodiment, the p-type ZnSeTe contact layer 118 is formed by forming a p-type AuPd electrode 120 in a stripe region on the p-type ZnSeTe contact layer 118 before forming the ZnO insulating layer 119 and performing a heat treatment.
And the p-type AuPd electrode 120 are alloyed, and an electrode having high adhesion and ohmic contact with the stripe region can be obtained.

Further, since the Ni electrode 122 has high reactivity with the oxide film and strongly adheres to the ZnO insulating layer 119 thereunder, the p-type second electrode 121 can prevent the electrode from peeling off. , Yield can be improved.

Next, FIG. 2 shows an example of a manufacturing process. In this embodiment, a molecular beam epitaxy method is used as a method for growing a ZnSe-based II-VI compound semiconductor.

First, a GaAs buffer layer 112, a Cl-doped n-type ZnMgSSe cladding layer 113, a Cl-doped n-type ZnSSe optical waveguide layer 114, a ZnCdSe active layer 115, and an N-doped p-type ZnSSe light guide are formed on a GaAs substrate 111. Wave layer 116, N-doped p-type ZnMgSSe cladding layer 117, N-doped p +
The type ZnSeTe contact layer 118 is sequentially epitaxially grown.

Next, a p-type ZnSeTe layer 1 doped with N
After the entire surface of the Pd / Au electrode 120 is vapor-deposited on the Pd / Au 18, a stripe-shaped resist pattern is formed on the Pd / Au electrode 120 by photolithography, and etching is performed using the same as a mask. The Pd / Au electrode 120 and the N + -doped p + type ZnSeTe layer 118 in a region other than under the stripe-shaped resist mask, and the N-doped p
A part of the type ZnMgSSe cladding layer 117 is removed by etching.

In this embodiment, the Pd / Au electrode 120 is removed by using a potassium iodide solution and N-doped p-type ZnSe.
To remove the Te layer 118 and the N-doped p-type ZnMgSSe cladding layer 117, etching was performed using a mixed solution of saturated bromine water, phosphoric acid, and water.

Next, after removing the resist, an n-type electrode is formed. In order to obtain an ohmic contact between the p-type ZnSeTe contact layer 118 and the AuPd electrode 120, for example, 2
A heat treatment at about 00 ° C. is performed.

Next, a ZnO insulating layer 119 is formed by a sputtering method. A stripe-shaped resist pattern is formed again on the ZnO insulating layer 119 by photolithography, and the ZnO insulating layer 119 is formed using the resist pattern as a mask.
Is formed by etching.

Next, a p-type second electrode 121 is formed on the entire surface of the wafer by using a vacuum evaporation method, thereby completing the device.

In this step, since the sputtering method is used, even if the substrate is not heated, the p-type semiconductor of the II-VI group semiconductor can be used.
Originally, strong adhesion between the ZnMgSSe layer 117 and the ZnO insulating film 119 is obtained. In addition, since heat treatment for obtaining ohmic contact with the p-type electrode is performed before the deposition of the ZnO insulating layer 119, the n-type GaAs substrate 111 is mainly
P-type ZnMg caused by a difference in thermal expansion coefficient from the insulating layer 119
The separation between the SSe layer 117 and the ZnO insulating layer 119 after the heat treatment can be prevented.

As described with reference to FIG. 1, since the adhesion between the p-type second electrode 121 and the ZnO insulating layer 119 is also strengthened by the Ni electrode 122, the p-type second electrode 12
1 and the ZnO insulating layer 119 can be simultaneously suppressed.
As a result, a current constriction stripe structure excellent in heat dissipation effect can be stably manufactured, and a blue-green semiconductor laser excellent in element characteristics and yield can be realized.

In this embodiment, Z is used as the insulating layer.
Although nO was used, similar effects can be obtained by using Al ₂ O ₃ 140 and ZnS 141 instead of ZnO as shown in FIGS. As shown in FIGS. 5 and 6, the p-type second electrode is made of Ti / Au142 or Cr / Au1 in addition to Ni / Au.
44 or the like.

(Embodiment 2) FIG. 7 shows a ZnSe II-
1 shows a structural cross-sectional view of a blue-green semiconductor laser using a group VI semiconductor. 111 is an n-type GaAs substrate doped with Si,
Reference numeral 112 denotes an n-type GaAs buffer layer doped with Si,
13 is an n-type ZnMgSSe cladding layer doped with Cl, 114 is an n-type ZnSSe optical waveguide layer doped with Cl, 115 is a ZnCdSe active layer, 116 is a p-type ZnSSe optical waveguide layer doped with N, and 117 is N-doped p-type ZnMgSSe cladding layer, 118 is p-type ZnSe
Te contact layer, 119 is a ZnO insulating layer, 120 is A
A p-type first electrode composed of two layers of u and Pd, 121 is a p-type second electrode composed of two layers of a Ti electrode 122 and an Au electrode 123
The electrode 124 is an n-type electrode made of AuGeNi.

In this embodiment, the p-type ZnSeTe contact layer is formed in a stripe region on the p-type ZnSeTe contact layer before the formation of the ZnO insulating layer.
A p-type AuPd electrode 120 is formed, and a p-type Ni electrode 230 is formed on the p-type AuPd electrode 120 as an etching mask.
And performing dry etching, a high-performance ridge stripe type current confinement structure can be formed. Accordingly, since the lateral diffusion current is suppressed, a single transverse mode laser can be manufactured.

Next, FIG. 8 shows an example of a manufacturing process. In this embodiment, a molecular beam epitaxy method is used as a method for growing a ZnSe-based II-VI compound semiconductor.

First, a GaAs buffer layer 112, a Cl-doped n-type ZnMgSSe cladding layer 113, a Cl-doped n-type ZnSSe optical waveguide layer 114, a ZnCdSe active layer 115, and an N-doped p-type ZnSSe light guide are formed on a GaAs substrate 111. Wave layer 116, N-doped p-type ZnMgSSe cladding layer 117, N-doped p +
The type ZnSeTe contact layer 118 is sequentially epitaxially grown. Next, a p-type ZnSeTe layer 1 doped with N
A Pd / Au electrode 120 is deposited on the entire surface of
/ P-type Ni electrode 2 of about 0.1 μm on Au electrode 120
30 is deposited on the entire surface.

Then, a striped resist pattern is formed on the p-type Ni electrode 230 by photolithography, and etching is performed using the same as a mask. The p-type Ni electrode 230 in a region other than under the stripe-shaped resist mask is removed by etching.

In this embodiment, the p-type Ni electrode 230 is removed by etching using a potassium iodide solution. Next, after removing the resist, an n-type electrode is formed, and p-type ZnS
In order to obtain ohmic contact between the eTe contact layer 118 and the AuPd electrode 120, for example, a heat treatment at about 200 ° C. is performed.

Next, etching is performed using the p-type Ni electrode 230 as a mask for dry etching. Pd / Au electrode 1 in a region other than under stripe-shaped p-type Ni electrode 230
20+ N-doped p + type ZnSeTe layer 118, N
A part of the p-type ZnMgSSe clad layer 117 doped with is removed by dry etching. A mixed gas of chlorine and hydrogen was used as an etching gas.

The etching gas is introduced at a controlled flow rate by a mass flow controller. Typical flow rates of chlorine and hydrogen are 5 sccm and 4 sccm, respectively.
The total gas pressure is 1 × 10 ⁻³ Torr. ECR plasma is a microwave of 2.45 GHz and EC of 875 G
It is generated by the R magnetic field. Microwave power is 2
00W and the extraction voltage were 300V. The microwave reflected wave was 0W. H to remove damaged area
Cl: H2O = 1: 1, and wet etching is performed for 1 minute. The stripe width was about 5 μm.
Next, a ZnO insulating layer 119 is formed by a sputtering method.

A stripe-shaped resist pattern is formed again on the ZnO insulating layer 119 by photolithography, and the ZnO insulating layer 119 is formed using the resist pattern as a mask.
Is formed by etching. Next, a p-type second electrode 121 is formed on the entire surface of the wafer by using a vacuum deposition method, thereby completing the device.

In this step, a dry etching method using chlorine gas plasma was used at the time of forming the current confinement structure. By this, the controllability of the etching depth for the ZnSSe / ZnMgSSe heterostructure is much higher than in the case of wet etching. improves. Furthermore, N can provide a large selectivity to dry etching using chlorine gas plasma.
Since the i-electrode 230 is used as a mask, a smooth vertical etching side wall can be obtained without receding the mask. As a result, light confinement is improved, and laser characteristics such as a single transverse mode and a lower threshold are obtained.

In this embodiment, Z is used as the insulating layer.
It was used nO FIG _3, Al ₂ O 3 14 4
0, ZnS141 can provide the same effect. As shown in FIGS. 5 and 6, the p-type second electrode may be Ti / Au142, Cr / Au144 or the like in addition to Ni / Au.

[0039]

As described above, according to the present invention, before forming the insulating layer, the contact layer and the p-type first electrode such as PdAu are subjected to a heat treatment, and Ni, Ti, Cr or the like is formed on the insulating film. The use of the electrode has the effect of improving the adhesion between the electrode and the contact layer and between the electrode and the insulating film. Therefore, in the ZnSe-based blue-green semiconductor light emitting device, a low threshold current, a long life, and the like can be realized.

[Brief description of the drawings]

FIG. 1 is a sectional structural view of a blue-green semiconductor laser device

FIG. 2 is a sectional view of a manufacturing process of a blue-green semiconductor laser device.

FIG. 3 is a sectional structural view of a blue-green semiconductor laser device;

FIG. 4 is a sectional structural view of a blue-green semiconductor laser device;

FIG. 5 is a sectional structural view of a blue-green semiconductor laser device;

FIG. 6 is a sectional structural view of a blue-green semiconductor laser device;

FIG. 7 is a sectional structural view of a blue-green semiconductor laser device;

FIG. 8 is a sectional view of a manufacturing process of a blue-green semiconductor laser device.

FIG. 9 is a structural sectional view of a conventional blue-green semiconductor laser device.

[Explanation of symbols]

 111 n-GaAs substrate 112 n-GaAs buffer layer 113 n-ZnMgSSe cladding layer 114 n-ZnSSe optical waveguide layer 115 ZnCdSe active layer 116 p-ZnSSe optical waveguide layer 117 p-ZnMgSSe cladding layer 118 p + -ZnSeTe contact layer 119 ZnO insulation Layer 120 p-Pd / Au first electrode 121 p-second electrode 122 p-Ni electrode 123 p-Au electrode 124 n-AuGeNi electrode 131 opening 140 Al2O3 insulating layer 141 ZnS insulating layer 142 p-second electrode 143 p -Ti electrode 144 p-second electrode 145 p-Cr electrode 230 p-Ni electrode

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shigeo Yoshii 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (10)

[Claims] 1. An active region formed of a II-VI compound semiconductor, a contact layer formed on the active region, and a first stripe-shaped electrode for obtaining ohmic contact with the contact layer. An insulating film deposited on a side region of the stripe electrode;
And a second p-type electrode formed on the insulating film and the first electrode and having high adhesion. 2. An insulating film containing ZnO or Al ₂ O ₃ ,
2. The method according to claim 1, wherein the second electrode includes one of Ni, Ti, and Cr.
3. The semiconductor light emitting device according to item 1. Forming an active region; forming a contact layer on the active region; forming the contact layer and a first electrode to obtain an ohmic contact by heat treatment; A method for manufacturing a semiconductor light emitting device, comprising: a step of depositing an insulating film on a side portion of a first electrode and a step of forming a second electrode on the insulating film. 4. The method according to claim 3, further comprising the step of forming the insulating film by a sputtering method without heating the substrate. 5. The method according to claim 3, wherein a heat treatment step is not included after the step of depositing the insulating film. 6. An active region formed of a II-VI compound semiconductor, a contact layer formed on the active region, and a first stripe-shaped electrode for obtaining ohmic contact with the contact layer. An electrode containing Ni on the stripe electrode, an insulating film deposited on a side region of the stripe electrode, and a second electrode formed on the Ni electrode and the insulating film and having high adhesion to the Ni electrode. A semiconductor light emitting device having a p-type electrode. 7. The insulating film contains ZnO or Al ₂ O ₃ ,
7. The second electrode contains Ti or Cr instead of Ni.
3. The semiconductor light emitting device according to item 1. 8. A step of performing dry etching using chlorine gas, a heat treatment step for obtaining ohmic contact after the dry etching step, a step of depositing an insulating film after the heat treatment step, A method for manufacturing a semiconductor light emitting device, comprising a step of forming a second electrode. 9. A step of forming a striped first electrode for obtaining ohmic contact, a step of forming a striped Ni electrode on the striped electrode, a step of performing etching after forming the electrode, and a step of forming an ohmic contact. A method for manufacturing a semiconductor light emitting device, comprising: a heat treatment step for obtaining a semiconductor substrate; a step of depositing an insulating film after the heat treatment step; and a step of forming a second electrode on the insulating film. 10. The method for manufacturing a semiconductor light emitting device according to claim 8, wherein no heat treatment step is included after the step of depositing the insulating film.