JPS589387A - Semiconductor laser device - Google Patents

Abstract

PURPOSE:To obtain a large laser output by a method wherein, in the case of the laser device having a lateral junction stripe structure, the horizontal angle of emission is symmetrized by flattening the density distribution of the active region in an active layer which is called carrier density distribution in other words. CONSTITUTION:An N type Ga0.65Al0.35As first clad layer 2, a Ga0.9Al0.1As active layer 3, and the second clad layer 4 of the same composition as the layer 1 are formed by lamination on a GaAs substrate 1, and the forbidden band width of the layer 3 is narrowered than that of the layers 2 and 4. Then, a P<+> type region 5 is formed by diffusing P type impurities on a part of the surface of the layer 4 in such a manner that the P type impurities will be entering into the substrate 1, a shallow P type region 6a which comes in contact with the region 5 is provided and this stripe region is used as an active region 10a. Subsequently, a P-side electrode 8 and an N-side electrode 9 are coated on both sides of the region 10a respectively while a part of region 10a is being exposed. Accordingly, as a part having different impurity density is not existed on the region 5, the current which does not contribute to oscillation is reduced, and the output of the title device can be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement of a lateral junction stripe (hereinafter abbreviated as "T" or "rsJ") laser device, which is a type of semiconductor laser device.

It is desirable to reduce the threshold current that causes laser oscillation in a semiconductor laser device, and several structures for this purpose are known.
A T, rEI laser device capable of long-life operation exceeding 0.6 hours is particularly excellent.

Figure 1 is a cross-sectional view showing an example of the structure of a conventional TJS laser device, in which (1) is a semi-insulating gallium-arsenide (GaAs) substrate, (2) is a gallium-aluminum-arsenide (Ga
1-x) A first cladding layer consisting of At, A8) layer, (
3) is an active layer consisting of a Ga(s-,)At, As layer;
(4) is a second cladding layer consisting of Ga(1-,)mut and As layers, and the constants xty and 2 are set as follows.

0≦y (x * z (1) Therefore, the forbidden band width of the active layer (3) is the same as that of the first cladding layer (2
) and the forbidden band width of the second cladding layer (4). (
5) is a high concentration p type impurity diffusion (p+ type) region, (6) is a low concentration p type impurity diffusion (p type) region, (7) is an n shadow region, (8) is a p electrode, and (9) is a n electrode, a*#i active layer (
3) consists of a low concentration A-type impurity diffusion region formed in
This is the active region where laser oscillation occurs.

By the way, in this conventional T, T8 laser device, the p-type impurity is diffused in the p-shade region (6) constituting the active region (a) to such a high concentration that the diffusion tip reaches the GaAs substrate (1). After forming the p+ 10-shaped region 5), heat treatment is performed at a temperature higher than the diffusion temperature.

Therefore, from the p + 10-shaped region 5) of the active layer (3) through the active region αQ consisting of the p shadow region (6), the n shadow region (7
) is as shown in FIG. 2M, and the corresponding refractive index distribution is as shown in FIG. 2B. Therefore, the conventional T, rS laser device has the following drawbacks.

(a) Since the refractive index change from the p shadow region (6) to the p+ decagonal region 5) is gradual, the p shadow region (6) of light is
) is insufficiently confined, and tends to extend toward the p+ decagonal region 5). As a result, the horizontal radiation angle pattern becomes asymmetric.

(b) The injected carriers recombine in the p shadow region (6) and contribute to laser oscillation, but the refractive index near the pn junction is higher than the position where this recombination is maximum, so light is confined. It is easy to cause poor oscillation and difficult to oscillate.

(c) Since the carrier density distribution in the p shadow region (6) has a shape as shown in Figure 2A, the p+ dec-shaped region 5)
Among the holes injected from the p-shade region (6), many of the holes do not recombine in the p-shade region (6) but recombine in the n-shade region (7), resulting in wasted current components.

This invention was made in view of the above points, and by adopting a configuration in which the carrier density distribution in the active region is flat, the horizontal radiation angle pattern has good symmetry, and there are fewer unnecessary current components. The objective is to obtain a semiconductor laser device that can obtain a large laser output.

Figure JILA is a sectional view showing the structure of a T,78 laser device which is an embodiment of the present invention, and parts equivalent to those of the conventional example in FIG. 1 are designated by the same reference numerals. The first cladding layer (2) and the second cladding layer (4) are Ga0J5 AZo, 3sAI! The active layer (3) is composed of both cladding layers (2) and (4).
) is composed of a Ga (1, gAt., IAB layer) with a narrow forbidden band width.
The p-type region (6a) is formed such that the impurity concentration in the p-type region (5
), the stripe width is 4 μm, and the stripe width is 4 μm. ) is a p-shaded region formed such that the impurity concentration at 8×1o18/cm3.

In the device of this embodiment, in the active region 4, a low concentration p-type impurity region is formed over the regions (5) and (6a) shown in the figure, and later, this low concentration p-type impurity region corresponds to the active region (6). The p1 region (5) is formed by diffusing p-type impurities at a higher concentration, leaving the width portion intact. Therefore, the carrier density distribution in the active layer (3) becomes flat in the p shadow region, that is, in the active region αQ, as shown in FIG. 4A. Therefore, there are the following effects.

B) The refractive index is flat near the position where the recombination of the injected carriers contributing to laser oscillation is maximum, that is, the p-shadow region (6a), as shown in FIG. 4B. The spread toward the 7) side and the p+ decagonal region 5) side is symmetrical, that is, the horizontal radiation angle is symmetrical.

(b) Holes injected from the p shadow region (5) recombine #1 in the p shadow region (6a), so the holes injected from the p shadow region (7)
There is less wasted current component due to carrier recombination.

e→ Since the width of the active region 000 can be widened, a large output can be obtained.

In addition, in the above embodiment, the diffusion tip of the p shadow region (6 m) is stopped within the first cladding layer (2), but this diffusion tip may be structured to reach as far as the Ga layer substrate (1). Of course.

As detailed above, the TJS laser device according to the present invention has a structure in which the impurity concentration distribution in the active region in the active layer, that is, the carrier density distribution is flat, so that the horizontal radiation angle of the laser emitted light is symmetrical. , current components that do not contribute to oscillation are reduced, and a large laser output can be obtained.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view showing an example of the structure of a conventional TJS laser device, Figure 2 is a diagram showing its carrier density distribution,
Fig. B is a diagram showing the refractive index distribution, and Fig. 3 is a cross-sectional view showing the structure of a TJ8 laser device, which is an embodiment of the present invention.
FIG. 4A is a diagram showing the carrier density distribution in this example, and FIG. 4B is a diagram similarly showing the refractive index distribution. In the figure, (1) is the substrate, (2) is the first cladding layer,
(3) is the active layer, (4) is the second cladding layer, (5) is the p
+ shape region (high concentration impurity diffusion region), (6a) is the p shadow region (low concentration impurity diffusion region'g@ru. In addition, the same reference numerals in the figure indicate the same or equivalent parts. Agent Makoto Kuzuno - ( Figure 1 Figure 2 Figure 31A Figure 4 Procedural amendment (self 11) Commissioner of the Japan Patent Office 1, Indication of the case Patent application No. 10616v 1987 2
, Title of the invention Cattle conductor laser device 3, Relationship with the case of the person making the amendment Patent applicant 5, Column 6.11 Detailed explanation of the invention in the specification subject to amendment 6.11 Correct contents Page 6 of the specification, No. 1 In rows 6 and 17, "active region QQ J" is replaced with "active region (10a).
Correct it with J. that's all

Claims (3)

[Claims] (1) One of the semiconductor substrates formed by sequentially forming an 1s1 cladding layer having a first conductivity type, an active layer having the first conductivity type, and a second cladding layer having the first conductivity type on a semi-insulating semiconductor substrate. forming a low-concentration impurity diffusion region having a jI2 conductivity type in a side surface portion such that a second conductivity type impurity tube diffuses from the surface of the second cladding layer so that the diffusion tip thereof reaches at least the first cladding layer; The second conductivity type impurity is further diffused from a part of the surface of the low concentration impurity diffusion region that is not adjacent to the first conductivity type second cladding layer, and the diffusion tip thereof reaches at least the above ml$ cladding layer. What is claimed is: 1. A semiconductor laser device characterized in that a high concentration impurity diffusion region having a second conductivity type is formed. (2) The semiconductor substrate is a gallium arsenide substrate, the active layer is a first gallium aluminum arsenide layer, and the first and second cladding layers each have a forbidden band width smaller than that of the first gallium aluminum arsenide layer. 2. The semiconductor laser device according to claim 1, characterized in that the second and third wide gallium-aluminum-arsenide layers are used. (3) Patent WI featuring ζ7 in which the impurity concentration sand in the active layer of the low-concentration impurity diffusion region is less than 10"70m3, and the impurity concentration in the active layer of the high-concentration impurity diffusion region is 2X10"7cm3 or more! A semiconductor laser device according to claim 1 or 2.