JPS6373692A - Manufacture of semiconductor laser device - Google Patents

Abstract

PURPOSE:To improve the bondability of assembling and efficiently escape the heat generated by flattening a completely grown layer surface by altering the crystal growing conditions of the uppermost layer in the formation of a thin multilayer film having a double hetero structure including the active layer on a substrate having an even part. CONSTITUTION:A photomask 10 is so formed as to form a stripe on an n-type GaAs substrate 2, and a ridge is formed by chemical etching. Then, an n-type GaAs buffer layer 3, an n-type AlyGa1-yAs clad layer 4, a nondoped AlxGa1-xAs active layer 5, a p-type AlyGa1-yAs clad layer 6, and an n-type AlzGa1-zAs buried layer 7 are sequentially grown. Then, the shape of the surface of the layer 7 is formed with an uneven surface by reflecting the shape of the substrate 2. An n-type GaAs cap layer 8 formed thereon is increased at the growing velocity and the molar ratio of the group V element with respect to group III element to flatten the surface of the grown layer. Then, Zn is diffused at 11 to the layer 6 at the top of the ridge at the center, and n-type and p-type electrodes 1, 9 are formed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method of manufacturing 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.

2. Description of the Related Art One of the important performances required of a semiconductor laser as a coherent light source for electronic equipment and optical equipment is single-transverse mode oscillation. To achieve this, it is necessary to suppress the spread of the current flowing through the laser element so as to concentrate it near the active region where the laser light propagates, and to confine the light. Such a semiconductor laser is usually called a stripe type laser. A buried stripe type semiconductor laser is a laser that can achieve the lowest threshold value and oscillates in a single transverse mode.

Normally, two crystal growth steps are required to fabricate a buried semiconductor laser. Also, recently, a buried laser has been shown in which a convex ridge is provided on a substrate and is constructed on the ridge.

Problems to be Solved by the Invention However, in a buried semiconductor laser fabricated by providing a ridge on a substrate and performing one crystal growth, the grown surface becomes convex reflecting the shape of the substrate.

When assembled upside down, not only the adhesion is poor, but also the heat generated by the laser operation cannot be efficiently dissipated, which has a negative effect on reliability.

In view of the above drawbacks, the present invention can be produced by one crystal growth,
In addition, the present invention provides a method for manufacturing a semiconductor laser device in which the grown surface can be flattened, bonding can be performed with good adhesion, and heat generated by laser operation can be efficiently dissipated.

Means for Solving the Problems In order to solve the above-mentioned problems, a method for manufacturing a semiconductor laser device according to the present invention includes forming two recesses facing each other on a substrate of one conductivity type, and forming a gap between the two recesses. A striped convex portion is formed on the substrate, and a multilayer thin film having a double heterostructure including an active layer is formed on the substrate by MOCVD, and at least up to the thin film layer directly above the active layer on both sides of the convex portion. In this method, a multilayer thin film is formed outside the same head in the stacking direction independently of the above-mentioned convex part, and at least only the top layer is formed at an increased growth rate, so that a part of the film exhibits a conductivity type opposite to the above-mentioned one conductivity type. It consists of forming areas.

Function When crystal growth is performed using the MOCVD method on a substrate having uneven portions, the shape of the surface of the growth layer changes depending on the growth conditions. ■ for group elements with increased A8H3 flow rate
When the ratio of group elements is increased, the layer grown on the uneven substrate grows to fill the unevenness on the substrate. By optimizing crystal growth conditions, it is possible to flatten the surface of a layer grown on a substrate having uneven parts.

In this way, even if a convex portion is provided on the substrate and crystal growth is performed, a semiconductor laser with a flat surface can be manufactured.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 shows a cross-sectional view of a semiconductor laser device in an embodiment of the present invention. In FIG. 1, 1 is the n-side electrode;
2 is an n-type GaAs substrate, 3 is an n-type GaAs 7771 layer,
4 is an n-type AlGaAs cladding layer, 6 is a non-doped AI
GaAs active layer, 6 p-type AIG aAts cladding layer, 7 n-type AlGaAs buried layer, 8! An l'in type GaAs cap layer, 9 a p-side electrode, and 11 a Zn diffusion region.

Next, a specific manufacturing method of the present invention will be explained.

First, as shown in FIG. 2(-), a photomask 10 is formed on the (100) plane of an n-type GaAs substrate 2 so as to form stripes of 8 .mu.m at intervals of 8 .mu.m.

Next, as shown in FIG. 2(b), etching is performed to a depth of 2.0 pm by chemical etching (for example, H2SO4:H2o2=H2o=1:828) to form a ridge parallel to the <011) direction.

Next, by the MOCVD method, an n-type GaAs buffer layer 3 (thickness o, 6 pm), an n-type AJyGa1-Ag craft layer 4 (y=o, 3 thickness 1.0 μm), and a non-doped Alx
""1-XA" active layer 5 (x = 0.1. Thickness 0.1 μm
), p-type Al yGa 1+ , Ats cladding layer 6
(7=0.3, thickness 1.1can), n-type A12Ga,
-, under the As buried layer (Z=0.3, thickness 1.571 m
) to grow sequentially. - For example, the crystal growth conditions are a growth rate of 4 μm/hour, a growth temperature of SOO''C2, and a molar ratio of group III elements to group III elements (III/V ratio) of 60. 8 (thickness 0.5μ
m) to grow. - For example, the crystal growth conditions are: growth rate 10 μm/hour, growth temperature 800″C, I [l/V ratio is 1
It is oo. Since the n-type GaAs substrate 2 is provided with a ridge, growth occurs independently on the upper part of the ridge and on the other parts. Furthermore, growth occurs at the ridge edge while exposing the (111) plane, and the growth rate is fast in the vicinity. Therefore, the buried layer 7 grows so that the upper part of the burr and the other part are connected. However, the shape of the surface of the buried layer 7 reflects the shape of the n-type GaAs substrate 2 and has irregularities. Even if the n-type GaAs cap layer 7 is grown on top of this under the same crystal growth conditions, the surface will still remain uneven, but by increasing the growth rate and vym ratio as described above, the surface of the grown layer can be made flat. can be converted into

Next, Zn diffusion 11 is performed to the p-type klGaAs cladding layer 6 on the upper part of the center glue, and finally the n-side and p-side electrodes 1
,9 are formed. When current is injected, the current is n-type GaA
It is narrowed at the top and bottom by the ridge portion on the s-substrate 2 and the p-type region formed by the Zn diffusion 11. As a result, 30m
A semiconductor laser device that oscillates in a single transverse mode at a threshold current value of A was obtained. In addition, as in the present invention, n-type GaAs
Since the edges provided on the substrate 2 are also provided outside the area where the actual laser operation is performed, the shape of the growth surface can be more easily flattened than when grown on a single edge. As mentioned above, the growth surface is flattened and the laser is turned up.
When assembled side down, problems such as poor adhesion during bonding and poor heat dissipation are eliminated.

In this embodiment, GaAs and AlGaAs semiconductor lasers have been described, but the present invention can be similarly applied to semiconductor lasers made of compound semiconductors including InP and other multi-component mixed crystal systems.

Alternatively, a p-type substrate may be used as the conductive substrate, and current stripes may be formed by ion implantation. Furthermore, MOCVD method was used for crystal growth in the example.

MBE method may also be used.

Effects of the Invention As described above, the feature of the present invention is that a convex portion is provided on the substrate, and convex portions are provided on both sides of the convex portion via concave portions.

In a semiconductor laser in which a double heterostructure including an active layer is formed by the MOCVD method, the crystal growth conditions of the top layer are changed to completely flatten the surface of the grown layer. With the structure of the present invention, a buried laser with a flat growth layer surface can be produced by one crystal growth, and when assembled upside down.

It can be bonded with perfect adhesion, and the heat generated by laser operation can be efficiently dissipated.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a semiconductor laser device according to an embodiment of the present invention, and FIG. 2(a), Φ) is a diagram showing the manufacturing process thereof. 1...n-side electrode, 2...n-type GaAs
Substrate, 3... One layer of n-type GaAs buffer, 4...
...N-type AlGaAs cladding layer, 6...
Non-doped AlGaAs active layer, 6... p-type A
lGaAs cladding layer, 7...n-type AlGaA
s-buried layer, 8...n-type GaAs cap layer, 9...p-side electrode, 1o...photomask, 11...Zn diffusion region. /-n vice ta 2--- n! ! eaAs↓Enoki3 ・-71'l hAs ) (-/ 7744---
n VAIGaAske 9 hood layer 5・-Ajt, aAs metallurgy b P type AIEraAS cryt, 47-n
WJ! AIEraAs embedding layer B-711 type & PoSki? Tube 1 2 77%' Cra As 甚, Plate/θ-Photomask Figure 2 ((1) (b)

Claims (1)

[Claims] Two recesses facing each other are formed on a substrate of one conductivity type, a striped protrusion is formed between the two recesses, and a multilayer thin film having a double heterostructure including an active layer is formed on the substrate by MOCVD. forming a multilayer thin film on both sides of the convex part, at least up to the thin film layer directly above the active layer, in the same order in the stacking direction and independently from the convex part, and at least the top layer is formed by increasing the growth rate. A method for manufacturing a semiconductor laser device, comprising: forming a region in which a portion thereof exhibits a conductivity type opposite to the one conductivity type.