JPS6178186A - Manufacture of semiconductor laser device - Google Patents

Abstract

PURPOSE:To prepare a semiconductor laser device having striped structure, into which a current constriction region is formed, with high yield in a wafer surface by burying a groove section so that film thickness on a flat section on a substrate reaches the depth or less of the central section of the groove section, shaping the surface of the groove section to a flat surface and forming double hetero-structure containing an active layer onto the flat surface. CONSTITUTION:An N type GaAs layer 2 is grown on the surface of a P type GaAs substrate 1, the surface is washed and treated, a photo-resist film 8 is attached onto the surface, and a striped groove is shaped through chemical etching treatment. The photo-resist film 8 is removed, the surface is washed and treated, and a crystal is grown on the substrate. The surface of a P type GaAlambdaAs clad layer is flattened through organic-metal vapor phase epitaxial growth at pressure of approximately 1atm.. A Ga1-xAlAs active layer 4 (0<=y<x), an N type Ga1-xAlxAs clad layer 5 and an N type GaAs cap layer 6 are grown continuously in succession. Crystal rowth is completed, ohmic electrodes 7 are prepared, and currents are injected.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a semiconductor laser device, which has been rapidly used as a light source for various electronic devices and optical devices in recent years and is in increasing demand.

Conventional configurations and their problems Important performance K, low current operation, and single-transverse mode oscillation are required of semiconductor lasers as coherent light sources for electronic and optical equipment. In order to realize these, it is necessary to suppress the spread of the trap and to confine the light so as to concentrate the current flowing through the laser element near the active region where the laser light propagates. A semiconductor laser having such a structure is usually called a stripe type semiconductor laser.

A relatively simple striping method uses only current constriction. Specifically, planar semiconductor lasers subjected to proton irradiation, those subjected to mu diffusion,
Examples include those in which an insulating film such as an oxide film is formed, and those in which a current narrowing region is created internally through constant pressure crystal growth. However, 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. For Zn diffusion type, 700-850"
Zn diffusion is often carried out at high temperatures such as °C (Z
There is a problem in that it is difficult to form a p/n junction as designed because dopanodes such as n move in the crystal. The method using an insulating film such as an oxide film has a weaker effect of narrowing the current in the manufactured semiconductor laser than the above two methods.

These striped semiconductor lasers are often manufactured using the LPE method, and the film thickness varies within the wafer surface, resulting in variations in device characteristics on the same wafer. Furthermore, when manufacturing a stripe type laser on a substrate with grooves formed therein, it is difficult to make the active layer smaller than 0.05 μm or to form a multi-quantum well type using the LPE method. In the MBE method, it is difficult to obtain a flat shrimp layer surface after crystal growth.

Purpose of the Invention In view of the above-mentioned drawbacks, the present invention aims to provide a manufacturing method for fabricating a semiconductor laser device having a stripe structure with a high yield in the same plane by creating a T-flow narrowing region inside by crystal growth or the like. purpose.

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 groove is formed so that it is deep in the center and gradually becomes shallower on the left and right sides to cut a part of the bond.
By the double growth method, the film thickness on the flat part of the substrate is
The groove is filled to a depth equal to or less than the depth of the center of the groove to form a flat surface, and a double heterostructure including an active layer is formed on the flat surface. Semiconductor laser devices that confine current and light in the vicinity and perform single-transverse mode oscillation and low-threshold current value operation can be manufactured at high yields with little variation in device characteristics within the surface. can.

DESCRIPTION OF EMBODIMENTS As an example, a method for manufacturing a semiconductor laser device according to the present invention will be specifically explained using an embodiment, in which a p-type GaAs substrate is used as a conductive substrate. As shown in FIG.
An n-type GaA tz layer 2 is grown to a thickness of 0.8 μm on the (1oO) plane of the rear ai, about 10 18 ax-'.

After the growth, the surface is cleaned, a photoresist film 8 is applied to the surface, and striped grooves are formed in the 110> direction by chemical etching. After removing the photoresist film 8 and cleaning the surface, crystal growth is performed on the substrate shown in FIG. The shape of the groove at this time is, for example, as shown in FIG. 2, with a depth h=1.2 μm and a width d=4 μm.

Metal organic vapor phase epitaxy (hereinafter referred to as MOCVD) is performed at a pressure of about 1 atmosphere. - growth temperature 7 as an example
70°C, [supply molar ratio of group element to group V element 40.
Total gas flow rate 6/! /min, and the growth rate is 12 μm/h. Under this condition, as shown in Figure 2, Kt2≦h (however,
t2: p-type G a A I A s film thickness at the flat part of the cladding layer h: depth of the groove), p-type G a A I A
s The surface of the layer becomes flat.

In this example, t2=O, Sμm. Furthermore, Ga 1-y Al y As active layer 4 (0≦y
≦X), thickness t 1=O-05Bm + n-type Q B1
-x Al x As cladding layer 5 of 1.5/l1m,
The thickness of the n-type GaAs cap layer 6 is 1.5 μm.
Grow sequentially. At this time, Ga 1-y Al y
As active layer 4 and n-type Ga 1-x Al x As
When growing the crystal layer 5, only the growth rate was changed to 2 μM during crystal growth. Like this MOC
In the VD method, by selecting the growth conditions, the grooves are filled with an appropriate film thickness so that the surface of the shrimp layer becomes a flat surface, and an active layer and quantum well structure of 0.05 μm or less are continuously formed on that surface. can.

After the crystal growth is completed, the ohmic electrode 7 is connected as shown in FIG.
and inject a current. The current is internal stripe width W
It flows in. Oscillation threshold current value is 45 mA, 60
Stable fundamental transverse mode oscillation with mA injection current, 5
A light output of mW was obtained.

In addition, in this example, GaAs system, GaAlA
Although the s-based semiconductor laser has been described, 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. As the crystal growth method, the MOCV D method, the IFC method, the MBE method, and the LPE method may be used in combination here. Furthermore, an n-type substrate may be used as the conductive substrate.

Effects of the Invention The present invention provides a semiconductor laser device that operates at low current and performs fundamental transverse mode oscillation, and has great practical effects.

[Brief explanation of the drawing]

FIG. 1(a), □□□) is a diagram for explaining the manufacturing process of the semiconductor laser device of the present invention, and FIG. 2 is a sectional view of the semiconductor laser device manufactured according to the present invention. 1...p-type GaAs substrate, 2...n-type GaAs current blocking layer, 3...p-type GaA
lAs cladding layer, 4...G a A I A
s Active layer, 5-...n-type Ga AI A
s craft layer, 6...n-type GaAs1ii, γ
...Ohmic electrode, 8...Photoresist film, d...Groove width, W...Internal stripe width, tl...Active layer Film thickness, h...
...Groove depth, t2 ...p-type G a A
I A s Film thickness at the flat part of the cladding layer. Name of agent: Patent attorney Toshio Nakao and one other person
d −0

Claims (1)

[Claims] A process of forming a groove deep in the center and gradually becoming shallower on the left and right sides so as to cut a part of the pn junction on a conductive substrate having a pn junction, and a process of forming a groove on the substrate by metal organic vapor phase epitaxial growth. a step of filling the groove so that the film thickness on the flat part is less than or equal to the depth of the center of the groove to form a semiconductor layer to form a flat surface; and an active layer on the flat surface. 1. A method for manufacturing a semiconductor laser device, comprising a step of forming a double heterostructure.