JPS60251687A - Manufacture of semiconductor laser device - Google Patents

Abstract

PURPOSE:To obtain a semiconductor laser device, which oscillates at a single transverse mode and operates at a low threshold, by removing one part of a thin-film layer, which is formed onto one conduction type semiconductor substrate with a stepped section and displays a conduction type reverse to the substrate, and shaping a multilayer thin-film containing double hetero-structure onto the thin-film layer through a liquid-phase epitaxial method. CONSTITUTION:A stepped section is formed in parallel in the <011> direction through photolithography onto the 100 face of a P type GaAs substrate 10. An N type GaAs current stopping layer 11 (carrier concentration: approximately 1X10<19>cm<-3>) is grown onto the stepped section in approximately 1mum through a MOCVD method. A photo-resist is applied, a photo-resist film 12 is left onto a surface in the upper section of the stepped section, and a surface shown in a broken line 20 is exposed through etching. The photo-resist film 12 is removed, the surface of the substrate is purified, a crystal is grown through a LPE method, a P type Ga1-xAlxAs clad layer 13, a Ga1-yAlyAs active layer 14, an N type Ga1-xAlxAs clad layer 15 and an N type GaAs layer 16 are shaped onto the surface shown in the broken line 20, and a grown surface is flattened.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for manufacturing a semiconductor laser device, whose use has been rapidly expanding in recent years as a light source for various electronic and electrical devices for consumer and industrial use. It is related to.

(Constitution of Conventional Example and Problems thereof) One of the important performances required of a semiconductor laser as a coherent light source for electronic equipment and optical equipment is oscillation in a single spot, that is, single-transverse mode oscillation. To achieve this, it is necessary to suppress the spread of the current flowing through the semiconductor laser device and to confine light near the active region. Such a semiconductor laser is generally called a striped semiconductor laser.

A relatively simple method for forming stripes is to use only current narrowing.

Specifically, examples include those in which a planar semiconductor laser is subjected to proton irradiation, one in which Zn is diffused, and one in which an insulating film such as an oxide film is formed. Each of these methods has significant drawbacks. When proton irradiation is applied, some crystals in each layer of the semiconductor laser are damaged during the proton irradiation, which may impair the characteristics of the semiconductor laser. In the case of the Zn diffusion type, processing is often performed at a high temperature of 700 to 850° C., and dopants such as Zn move in the crystal, making it possible to form stripes, but making narrow stripes difficult. The method using an insulating film such as an oxide film has a disadvantage in that the effect of narrowing the current in the manufactured semiconductor laser is weaker than the above two methods.

(Object of the Invention) In view of the above-mentioned drawbacks, the present invention provides a current limiting layer on a semiconductor substrate, configures a multilayer thin film including a double heterostructure on the current limiting layer, and creates a narrow space inside by the current limiting layer. A method of manufacturing a semiconductor laser device forming a striped structure is provided.

(Structure of the Invention) In order to achieve this object, the method for manufacturing a semiconductor laser device of the present invention provides a method for manufacturing a semiconductor laser device of the present invention.
A thin film layer having a conductivity type opposite to that of the substrate is formed using the MOC or VD method (metal-organic vapor phase epitaxy), and after removing a part of the thin film layer, a LPE method (liquid phase epitaxial growth method) is applied on top of it. It is constructed by forming a multilayer thin film containing a double heterostructure using a method (method). With this configuration, it is possible to easily realize a semiconductor laser device which has a current confining stripe inside and has single-transverse mode oscillation and low threshold operation.

(Description of Embodiment) Hereinafter, one embodiment of the present invention will be specifically described using the drawings.

As an example, a p-type GaAs substrate is used as the substrate. As shown in FIG. 1, steps are provided on the (ioo) plane of the p-type GaAs substrate 10 by photolithography in parallel to the <OTT> direction. At this time, the cross-sectional shape of the step becomes an inverted mesa shape. Next, on top of this, n-type GaAs was deposited using the MOCVD method.
Current blocking layer 11 (carrier concentration: 1×101gan-”
) is grown to a thickness of about 1 μm. The growth conditions at this time are
Growth rate 3 μm/hour, substrate temperature 650°C, V/m ratio 10
It is said that As shown in the figure, little growth occurs on the side surfaces of the protrusions of the step. Next, apply photoresist,
A photoresist film 12 is left on the surface above the step. )I2
Etching is performed using a So4-based etching solution to expose a surface as shown by the broken line 2o. As a result, an inverted mesa-shaped step with a depth h is formed on the flat substrate.

The reason why an inverted mesa-shaped substrate was used from the beginning was to facilitate mask alignment when forming steps later.

Thereafter, the photoresist film 12 is removed and the substrate surface is cleaned, followed by crystal growth using the LPE method. Crystal growth was performed at a growth temperature of 850°C, a supersaturation level of 7°C, and a cooling rate of 0.5°C/min. On the plane of the broken line 20 in FIG. 1, as shown in FIG. 2, p-type Ga1-XiXAs
Cladding layer 13, Ga□-, AN, As active layer 14 (0
≦y<x), n-type Ga1-x1xAs cladding layer 15,
An n-type GaAs layer 16 is formed so that the growth surface is flat.

When electrodes are formed on each surface of the p-type GaAs substrate 10 and the n-type GaAs layer 16 and a current is applied, the W as shown in FIG. Current is injected with a width of , achieving current narrowing. This is because the n-type GaAs layer 11 is made of p-type Ga, -XAI
This is because a p/n junction is formed with the XAs cladding layer 13, and the p/n junction becomes a reverse bias during current injection. As a result, a low threshold semiconductor laser device with W=2 μm and a threshold current of 20 mA was obtained. At this time,
At the same time, single-transverse mode oscillation was also achieved.

In this embodiment, GaAs-based and GaAlAs-based semiconductor lasers have been described, but the present invention can be similarly applied to semiconductor laser devices made of compound semiconductors including InP-based and other multi-component mixed crystal systems. can. Furthermore, the present invention can be similarly applied to the steps of the substrate by using a forward mesa shape.

(Effects of the Invention) As explained above, according to the present invention, at a low threshold,
A semiconductor laser device that oscillates in a single transverse mode can be easily manufactured, and its practical effects are remarkable.

[Brief Description of the Drawings] Fig. 1 is a cross-sectional view of a thin film layer crystal-grown on a stepped substrate by the MOCVD method according to an embodiment of the present invention, and Fig. 2 is a cross-sectional view of the same semiconductor laser device. be. 10- p-type GaAs substrate, 11- n-type GaAg current blocking layer, 12... photoresist film, 13... p-type GaAllAs cladding layer, 14- Ga1As active layer, 15''' n-type GaANAs cladding layer, 16
- n-type GaAs layer.

Claims (1)

[Claims] A thin film layer having a conductivity type opposite to that of the substrate is formed on a semiconductor substrate of one conductivity type having a step by MOCVD (metal organic chemical vapor deposition), and after removing a part of the thin film layer, A method for manufacturing a semiconductor laser device, characterized in that a multilayer thin film including a double heterostructure is formed by an LPE method (liquid phase epitaxial method).