JPS6373583A - Manufacture of semiconductor laser - Google Patents

Abstract

PURPOSE:To improve reliability, and to enable mass production by diffusing an impurity and controlling a transverse mode in a region, in which the impurity is not diffused, in a current injection section, removing a semiconductor layer in the surface prior to second crystal growth and forming a semiconductor layer containing an active layer. CONSTITUTION:Since a region 4 in which Zn is diffused to a superlattice layer 2 is constituted of P-type Al0.5Ga0.5As, and made transparent to laser beams, and the superlattice layer 2 absorbs laser beams, and takes an N type, current constriction and loss guide type transverse mode control are conducted in the same stripe. The layer structure of a crystal is all shaped in flat planar structure, thus improving reliability. Since a GaAs layer 3 is removed through vapor phase etching prior to second MOVPE growth, a semiconductor layer including an active layer can be laminated onto an extremely clean crystal surface, and crystal dislocation is reduced. An impurity may be diffused in depth that the superlattice layer is penetrated, and the conditions of the control of a diffusion are relaxed extremely, thus utilizing the mass productivity of an MOVPE method without being limited by other processes.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for manufacturing a semiconductor laser.

[Conventional technology]

2. Description of the Related Art In recent years, optical information processing using semiconductor lasers for digital audio discs, video discs, etc. has been widely used because of its advantages such as large capacity and random access. The semiconductor laser used here is required to oscillate in a stable fundamental transverse mode and have small astigmatism, but what is especially important is that it be excellent in mass production.

Here, Metal-Organic Vapor
Phase epitaxy method (hereinafter referred to as MOVP)
AlGaAs/G a A using the E method)
This will be explained using an example of an S semiconductor laser.

FIG. 3 is a cross-sectional view showing the configuration of an example of a conventional semiconductor laser (for example, rIEDM' 83 Procee
dings”, pp. 292-295), Figure 4 (a
) to (c) are cross-sectional views showing the manufacturing process. This semiconductor laser is first manufactured by MOVP on an n-type GaAs substrate 11.
N-type A10.45G a g, 55A 5 layers 12, AI 0.15G a 0-85AS active layer 1 by E method
3, p-type A] 0.45G a 0-55A 8 layers 1
4. The n-type GaAs current blocking layer 15 is sequentially laminated, and the etching layer 16 penetrating the n-type GaAs current blocking layer 15 is formed by selective etching (FIG. 4(a)).
b)), then p-type A 1 g,4 by MOVPE method
5 Ga 0.55A 3 layer 17, p-type GaAs layer 18 are formed (Fig. 4('C)), and finally n electrode 1 is formed.
9. The n-electrode 20 is formed to complete the semiconductor laser shown in FIG. In this semiconductor laser, the current is constricted by the current blocking layer 15, and the transverse mode of the laser beam is set as the fundamental mode due to the difference in effective light absorption rate between the groove 16 region and other regions.

[Problem that the invention seeks to solve]

In this way, conventional semiconductor lasers have a laser crystal with a full
6, stress is concentrated in the current injection region, that is, the laser oscillation region, which poses a problem in long-term reliability. Also, the second MOVPE growth is exposed to the atmosphere and the oxidized p-type A
I o, 45G a o-55A Since it is performed on 5 layers 14, p-type A I 0.45G a 0-55As
The layer 17 and the p-type GaAs layer 18 contain crystal dislocation, which affects the reliability of the laser.If this oxidation is severe, negative resistance is observed in the IV characteristics of the laser device. Furthermore, in manufacturing the laser, a p-type A 10.45G a with a layer thickness of about 0.3 μm is passed through the current blocking layer 15 for current injection.
, ), 55As must be carried out to such an extent that it does not penetrate the S layer 14, so requirements for controllability and uniformity of the formation of the trough 16 are extremely strict, which hinders mass production of lasers.

An object of the present invention is to solve these problems and provide a method for manufacturing a semiconductor laser that is highly reliable and suitable for mass production.

[Means for solving problems]

The structure of the present invention includes a superlattice layer in which a first semiconductor layer and a second semiconductor layer, each of which has a thickness of 200 Å or less and one of which is of a second conductivity type, are alternately laminated on a semiconductor substrate of a first conductivity type;
A third semiconductor layer of a first conductivity type, an active layer, and a fourth semiconductor layer of a second conductivity type are sequentially formed;
In the method for manufacturing a semiconductor laser in which a semiconductor layer, a fourth semiconductor layer has a larger band gap than the active layer, and the second semiconductor layer has a smaller band gap than the first semiconductor layer, a first epitaxial growth step of sequentially stacking a lattice layer and a fifth semiconductor layer to form a substrate crystal; and selectively applying a first conductive layer to a stripe-like region on the substrate crystal to a depth penetrating the superlattice layer. an impurity diffusion step of performing a type impurity diffusion; a step of removing the fifth semiconductor layer after the impurity diffusion; and a step of removing the fifth semiconductor layer.
the third semiconductor layer on the superlattice layer from which the semiconductor layer has been removed;
The method is characterized by including a second epitaxial growth step of sequentially forming the active layer and the fourth semiconductor layer.

[Effect]

In the semiconductor laser manufacturing method of the present invention, the structure is averaged when impurities are diffused into the superlattice layer, and the current injection part is made transparent to laser light by diffusing impurities. In the region where impurity diffusion is not performed, loss-guided transverse mode control is performed to absorb laser light, and prior to the second crystal growth, the semiconductor layer on the surface is removed to form a semiconductor containing an active layer on a clean crystal surface. By forming layers, a manufacturing method that is highly reliable and suitable for mass production can be obtained.

〔Example〕

Next, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a sectional view showing the structure of a semiconductor laser obtained according to an embodiment of the present invention, and FIGS. 2(a) to 2(d) are sectional views showing the manufacturing method thereof in order of steps. Introduction 1st MOV
A superlattice layer 2 and a GaAs layer 3 are formed on an n-type GaAs substrate 1 by PE growth, in which an AlAs layer with a thickness of 80 layers and an n-type GaA layer with a thickness of 80 layers are alternately laminated. 2
Figure (a)), then the superlattice layer is selected in two stripes Z
The impurity diffusion layer 4 is formed by performing n-diffusion.
)), prior to the second MOVPE growth, gas phase etching was performed using hydrogen chloride and arsine in the MOVPE reaction tube to remove the GaAs layer 3 (Fig. 2(C)), and the second MOVPE growth was performed. p-type A + 0.450 a
g, 55A s layer 5. Alo, tsG a O, 65A
S active layer 6. n-type A] 0.45G a 0-55
An AS layer 7 and an n-type GaAs layer 8 are formed (Fig. 2(d)).
), and finally an n-electrode 9 and an n-electrode 10 are formed to complete the semiconductor laser shown in FIG.

〔Effect of the invention〕

According to the semiconductor laser manufacturing method of this embodiment, the region 4 in which Zn is diffused into the superlattice layer 2 is p-type A1a, 5G a
o, 5 A s, transparent to laser light,
Furthermore, since the superlattice layer 2 absorbs laser light and is n-type, it has a self-aligned structure in which current confinement and loss-guided transverse mode control are performed in the same stripe. Furthermore, since the crystal layer structure is all a flat Brainer structure, no extra stress is applied to the active layer, making it possible to obtain a highly reliable semiconductor laser. Furthermore, since the GaAs layer 3 is removed by vapor phase etching prior to the second MOVPE growth, the semiconductor layer including the active layer can be stacked on an extremely clean crystal surface, making it possible to obtain a laser crystal with few crystal dislocations. . Furthermore, the depth of impurity diffusion only needs to penetrate the superlattice layer, and the conditions for controlling diffusion are extremely loose. Zunawachi, MOVPE
The mass productivity of the method can be utilized without being restricted to other processes.

In addition, in the description of the present invention, A
Although the explanation has been given using a lGaAs/GaAs semiconductor laser as an example, it goes without saying that the present invention can be applied to semiconductor lasers made of other materials using a normal phase outer length method or a molecular beam epitaxial method other than the MOVPE method.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a semiconductor laser obtained by an embodiment of the present invention, FIGS. 2(a) to (d) are cross-sectional views showing the manufacturing method in order of steps, and FIG. 3 is an example of a semiconductor laser according to the prior art. FIGS. 4(a) to 4(C) are cross-sectional views showing the manufacturing method in the order of steps. 1... n-type GaAs substrate, 2... superlattice layer, 3...
・GaAs layer, 4... impurity diffusion layer, 5.14.17
... p-type A l O, 45G a 0.55A 45
Layer, 6, 13·A iO. +50 a 0.85A S active layer, 7.12-n type A
+0.45G ao, 5sA 5 layers, 8.15-
n-type GaAs layer, 9.20...n electrode, 10.19.
...p electrode, 11...n-type GaAs substrate, 16-...
Groove, 18-n-type GaA5 layer. Kaya 1 illustration 2 times

Claims (1)

[Claims] A superlattice layer in which a first semiconductor layer and a second semiconductor layer, each of which has a thickness of 200 Å or less and one of which is a second conductivity type, is alternately laminated on a semiconductor substrate of a first conductivity type; 3
A semiconductor layer, an active layer, and a fourth semiconductor layer of a second conductivity type are sequentially formed, the first semiconductor layer, the third semiconductor layer, and the fourth semiconductor layer having a larger band gap than the active layer; The second semiconductor layer has a bandgap smaller than that of the first semiconductor layer. In the method for manufacturing a semiconductor laser, the superlattice layer and the fifth semiconductor layer are sequentially stacked on the semiconductor substrate to form a substrate crystal. an impurity diffusion step of selectively diffusing a first conductivity type impurity into a striped region on the substrate crystal to a depth penetrating the superlattice layer; and after this impurity diffusion, the fifth
A semiconductor comprising: a step of removing a semiconductor layer; and a second epitaxial growth step of sequentially forming the third semiconductor layer, the active layer, and the fourth semiconductor layer on the removed superlattice layer of the fifth semiconductor layer. Laser manufacturing method.