JPS63181492A - Semiconductor laser device - Google Patents

Abstract

PURPOSE:To suppress the crack development in the vicinity of an active layer and operate on a low electric current by having a structure where an N-type on a P-type substrate comprising a protruding mesa has two ridge forms that are adjacent to each other at the opposite side of the substrate and by preparing a groove part reaching the substrate between two ridges where an end of the groove and an end of the protruding mesa in the same direction to the center of the groove are separated, thereby forming multilayer thin films having a double-hetero structure including the active layer on the conductive substrate including the ridges. CONSTITUTION:Stripe-like protruding ridges are prepared on a P-type GaAs substrate 11 in the direction of <ITO> and an N-type GaAs current blocking layer 12 grows on the ridges. After the growth surface is treated by washing, the stripe-like protruding ridges that are adjacent to each other, thereby interposing the groove between the ridges in the direction of <ITO>, are provided and the groove between the ridges reaches the ridges. After washing the surface, a P-type AlxGa1-xAs layer 13, an AlyGa1-yAs active layer 14, an N-type AlxGa1-xAs clad layer 15 as well as an N-type can layer 16 grow in sequence under the same conditions. In such a case, intervals WSL and WSR between the ridge and V-shaped groove shall be more than 2mum. Thus a semiconductor laser device which performs uniformly basic transverse mode oscillations at a low threshold current value is obtained.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a semiconductor laser device.

BACKGROUND OF THE INVENTION Important performances required of semiconductor lasers as coherent light sources for electronic and optical equipment include low current operation and fundamental transverse mode oscillation. In order to achieve these performances, it is necessary to suppress the spread and confine the current flowing through the laser element so as to concentrate it near the active region where the laser light propagates. A semiconductor laser with such a structure built inside is usually called an internal stripe type laser. (For example, "Compound Semiconductor Devices (II)," edited by Tetsuji Imai et al., jp, p. 214-p., 215.) Hereinafter, with reference to the drawings, a BTR3 type laser will be described as an example of the conventional internal stripe type laser as described above. Raise it and explain.

FIG. 3 shows a schematic diagram of the cross-sectional shape of the BTR8 type laser.

In FIG. 3, 1 is a p-type GaAs substrate, 2 is an n-type GaAs substrate, and 2 is an n-type GaAs substrate.
Ag current blocking layer, 3 p-type AlGaAs cladding layer, 4
is A/GaAs active layer, 6 is n-type A, dGaAg layer.
6 is an n-type GaAs contact layer, 7 is an n-side ohmic electrode, and 8 is a p-side ohmic electrode.

The manufacturing method and operation of the BTR3 type laser constructed as described above will be briefly described below.The BTR3 type laser is manufactured by two liquid phase epitaxial growth processes.

p-type GaAa substrate 1 (carrier concentration=1018~10
By using a photomask and chemical etching, a convex ridge having a width of 10 μm as shown in FIG. 3 is provided in the form of a stripe in the (ITo) direction on the (100) plane of the (cm2). On this ridge, n-type GaA was grown by liquid phase epitaxial growth.
s Current blocking layer 2 is grown to a thickness of 0.8 μm. The growth conditions were a growth temperature of 850°C, a cooling rate of 0.6°C/min, and a supersaturation degree of 8°C. After cleaning the growth surface, a photomask and chemical etching process are used to form convex ridges in the form of stripes with a width of 20 μm adjacent to each other in the (ITo) direction, as shown in Figure 3, and grooves between the ridges are formed. Try to reach the above ridge. After surface cleaning treatment, p was grown using liquid phase epitaxial growth under the same growth conditions as above.
The type AlxGa1-rA8 layer 3 is O-3μrrx in the flat part.
, AII yGa 1□As active layer 4 (0≦y<x
) to 0.06 μm, n-type Al x Ga 1□As cladding layer 6 to 1.5 μm, and n-type GaAs cap layer 6 to 1.5 μm. Since crystal growth is performed on a substrate provided with two adjacent ridges, it is possible to grow the active layer within the active region with good controllability even if the thickness is 0.06 μm, and with good uniformity within the wafer surface.

Further, as shown in FIG. 3, n-side and p-side ohmic electrodes 7 and 8 are formed on the structure, and a current is injected. Since the current flows narrowly only in the V-shaped or U-shaped groove of the internal stripe portion, fundamental transverse mode oscillation occurs at a threshold of 25 mA.

Problems to be Solved by the Invention However, in the above-mentioned BTR3 type laser, cracks occur near the active region of the cross-sectional shape of the laser end face during the cleavage process to construct the laser resonator, as shown in FIG. This may occur. Note that cracks often occur from both interfaces of the n-type current blocking layer 2. The occurrence of this crack causes application problems such as a significant increase in the threshold current value and operating current value of the laser chip, deformation of the optical intensity distribution, and a decrease in coupling efficiency with optical components. .

In view of the above drawbacks, the present invention provides a semiconductor laser device which suppresses the occurrence of cracks near the active region, has a high yield, operates at a low current, and oscillates in a fundamental transverse mode.

Means for Solving the Problems In order to solve the above problems, the semiconductor laser device of the present invention includes an n-type layer on a p-type substrate having a convex mesa,
The n-type layer has two adjacent ridge shapes on the side opposite to the substrate, and a 7- or U-shaped groove portion reaching the substrate between the ridges is sb, with respect to the edge of the groove and the center of the groove. A multilayer thin film having a double heterostructure including an active layer on a conductive substrate including two ridges adjacent to the groove, wherein the ends of the convex mesas in the same direction are located at least 2 μm apart in both directions. configured.

This configuration has a uniform internal stripe structure,
A semiconductor laser device with a low threshold value, low current operation, and stable fundamental transverse mode oscillation can be realized.

EXAMPLES Hereinafter, examples of the present invention will be described with reference to the drawings.

FIG. 1 shows a sectional view of a semiconductor laser device according to an embodiment of the present invention.

In FIG. 1, 11 is a p-type GaAs substrate, 12 is an n-type GaAs current blocking layer, 13 is a p-type AlGaAs cladding layer, 14 is an AlGaAs active layer, and 15 is an n-type AlGaAs layer.
s cladding layer, 16 is n-type GaAs = 77 tact layer,
17 is an n-side ohmic electrode, and 18 is a p-side ohmic electrode.

Regarding the semiconductor laser device configured as described above, an example of its fabrication and operation results will be briefly described below.

As an example, the substrate is a p-type GaAs substrate 11 shown in FIG.
(Carrier concentration: 1018 to 1o19α-3) is used. On the (100) plane of this p-type GaAs substrate 11, a convex ridge having a width W1 of 30 μm as shown in FIG. 3 is provided in a stripe shape in the (ITo) direction by using a photomask and chemical etching. On this ridge, an n-type GaAs current blocking layer 12 of 0.8 μm was formed by liquid phase epitaxial growth.
It grows to a thickness of m. The growth conditions were a growth temperature of 860°C, a cooling rate of 0.5.07 minutes, and a supersaturation degree of 8°C.

After cleaning the growth surface, a photomask and chemical etching process are used to provide striped convex ridges with a width of 20 .mu.m adjacent to each other across a 6I.times.n groove in the (ITO') direction, as shown in FIG. The groove between the ridges should reach the ridge. After surface cleaning, p was grown by liquid phase epitaxial growth under the same growth conditions as above.
Mold Al engineering Ga1-! The AB layer 13 has a thickness of 0.3 μm in the flat part,
AlyGa1-A8 active layer 14 (0≦y<x) is 0
．． 06 pm Sn-type All x Ga 1- , an As cladding layer 15 with a thickness of 1.5 μm, and an n-type GaAs cap layer 16 with a thickness of 1.5 μm are sequentially grown.

Furthermore, as shown in FIG. 3, n-side and p-side ohmic electrodes 7 and 8 were formed on the structure, and a current was injected. Since the current flows constricted only in the V-shaped or U-shaped groove of the internal stripe portion, fundamental transverse mode oscillation was performed at a threshold of 25 mA. The crack occurrence rate near the active region within the wafer surface was approximately less than that of the conventional example, and the uniformity of the laser chip characteristics within the wafer surface was also improved.

It is thought that by widening the width of the ridge provided on the p-type GaAs+ substrate 11, the cracks that occurred as shown in FIG. 2 were moved away from the vicinity of the active region. As a result of the experiment, the distance between the ridge and the V-shaped groove in Fig. 1 is WSL≧2μ.
It was found that the same results as above can be obtained if m and WSR≧2 μm.

Effects of the Invention The present invention makes it possible to form an internal stripe-type laser structure with good uniformity within the wafer surface, and as a result, it is possible to create a semiconductor laser device with good uniformity and fundamental transverse mode oscillation with a low threshold current value. The practical effects of this are remarkable.

[Brief explanation of the drawing]

FIG. 3, which is a diagram showing how cracks occur, is a cross-sectional view of a conventional semiconductor laser device. 1.11...p-type GaAs substrate, 2,12...
...N-type GaAs current blocking layer, 3, 13...
-p-type AlGaAs cladding layer, 4, 14...
AlGaAs active layer, 5°15...n-type AlG
aAs cladding layer, 6, 16... n-type GaAs
Contact layer, 7.17...n-side ohmic electrode, 8.18...p-side ohmic electrode, 2o.
...Crack, 21...Near active region,
Wv...Width of the V-shaped groove, WR...Width of the ridge provided on the p-type substrate, WsL, WsR...
The distance between the ridge and the V-shaped groove.

Claims (1)

[Claims] On a substrate of one conductivity type having a convex portion, there is a layer of a conductivity type opposite to the one conductivity type having two adjacent ridges, and between the two ridges there is a V-shape or a layer that reaches the convex portion of the substrate. There is a U-shaped groove, the distance between the edge of the groove and the edge of the protrusion in the same direction with respect to the center of the groove is 2 μm or more, and an active layer is formed on the substrate including the groove and two ridges. 1. A semiconductor laser device comprising a multilayer thin film having a double heterostructure including layers.