JPH02268482A - Manufacture of buried semiconductor laser element - Google Patents

Abstract

PURPOSE:To elevate the crystal property of a current constriction layer so as to manufacture a laser element by forming a mesa stripe on a GaAs substrate, and thereon growing an epitaxial layer for double-hetero semiconductor laser, and growing a current constriction layer without using selective growth. CONSTITUTION:Etching is done using phosphoric acid etchant with the photoresist as a mask in the direction of <011> on the face (100) of an n-GaAs substrate 1 so as to form a mesa stripe 12. Next, the substrate 1 is carried in a MOCVD device, and epitaxial growth is performed, whereby an n-clad layer 2, a p-active layer 3, a p-clad layer 4, and a p contact layer are formed, in order on the mesa stripe 12. Subsequently, an Al0.45Ga0.55As layer 7 of high resistance is grown, and further an n-GaAs current constriction layer 6 is grown. Next, the substrate 1 is taken out of the MOCVD device, and the topside of the active layer is etched with the photoresist, etc., as a mask so as to expose the p contact layer 5. By performing wafer process, a semiconductor layer element is completed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a GaAs-A I GaAS double hetero embedded semiconductor laser device.

[Prior Art] Conventionally, a GaAs-A I GaAs double-hetero buried semiconductor laser device as shown in FIG. 3 has been proposed.

In this Figure 3, 1 is an n-Q&AS board, 2 is an n-
AIQaAS cladding layer, 0, 45 0.55 3 is p-AI Ga AS active layer, 4 is 0
．． 08 0.92 p-Δl Ga As cladding layer, 5 is 0
．． 45 0.55 p-GaAs contact layer 6, n-GaAS current confinement layers 10 and 11 are electrodes. This double hetero embedded type semiconductor laser device is a general double hetero semiconductor laser! T=J has excellent characteristics that cannot be obtained with A elements. In other words, the active region 3 has n-A with a relatively large mixed crystal ratio.
It has a structure surrounded by the lGaAs layer 2 and the p-AI (3a) Rad layer 4, and only a part of the active region 3 is roughly surrounded by the current confinement layer 6. No current flows, the oscillation threshold current is reduced, and the stability against current changes in the oscillation mode (main and transverse modes) is improved.Furthermore, by selecting the material for the current confinement layer 6, the current confinement is reduced. Layer 6 becomes a light absorption layer, making it possible to achieve high output.

In this way, the GaAs-AI GaAs double-hetero embedded type semiconductor Rayleigh device becomes a stable and high-output light source, so it can be used as a light source for optical information transmission and optical information processing.
1 telescope. However, the yield of producing 1q of devices that can exhibit these characteristics is extremely low, and the lifespan is short, so this poses an industrial problem.

The method shown in FIG. 4 is used as a method of manufacturing the embedded type semiconductor laser cable shown in FIG. 3.

First, n-=GaAsJiGaAs substrate 1 0.45
As cladding layer 4 (9 degrees sharp 1 degree 1 x 1018/
cm3 film thickness 1 = 5 μm>, D-GaAs contact 1~
Layer 5 (key concentration: 1 x 1018/Cm3, film thickness: 0.5 μm) is sequentially formed using the MOCVD method, and then an S + 02 layer 12 is formed on the p contact layer 5 by sputtering. A slit-like etching mask 8 is applied over the portion where a current path is to be formed using a well-known technique (FIG. 4(a)).

Next, the portions of the SI OZ layer 12 that are not protected by the etching mask 8 are first removed using buffered hydrofluoric acid, and then the portions of the p-contact layer 5 that are not protected by the etching mask 8 are removed using, for example, a phosphoric acid-based etching solution. After removing the unetched portions and subsequently removing a part of the p-Clarad layer 4 leaving a predetermined thickness, the etching mask 8 is removed (FIG. 4(b). In this way, the etching mask 8 is removed. 1~
The substrate on which the live pattern was formed was carried into the MOCVDI equipment again, and S! 02 layer 12 as a mask for selective growth
The G a AS current confinement layer 6 is grown using a selective filling growth method (FIG. 4(C)).

Then, 1q of epitaxial layers for a buried semiconductor laser element are obtained by removing S+02m12 with buffed fluoric acid (FIG. 4(d)).

Thereafter, by using a normal laser diode manufacturing process, it is possible to manufacture 1q of embedded semiconductor laser elements as shown in FIG.

[Problem to be Solved by the Invention 1] However, when manufacturing an embedded semiconductor layer element by the method described above, the following problems occurred.

First, selective filling growth for forming the current confinement layer 6 was difficult, and one molecular crystal was deposited on the 8102 layer 12, making it difficult to remove the mask material and resulting in low productivity. Furthermore, when etching is performed after the first epitaxial growth is completed and second epitaxial growth is performed, the p-Clarad layer 4 is once exposed to the atmosphere and oxidized, and as a result, the film quality of the second epitaxial layer is inferior, and some The current passed through the current confinement layer 6, increasing the triggering threshold.

In general, because the expansion coefficients of the 5102 layer 12 and GaAs are different, stress causes dislocations in the active layer 3 during the second epitaxial growth, and these dislocations shorten the life of the device.

[Means for Solving the Problems] The present invention involves forming a mesa stripe on a GaAs substrate by etching, growing a normal double-layer epitaxy layer on the mesa stripe, and further Subsequently, a current confinement layer is grown without using selective growth.

[Function] By using the present invention, a buried type semiconductor laser device can be manufactured without using selective growth, so that it has the following features.

First, the steps of forming and removing sio2m are eliminated. Furthermore, since the current confinement layer is grown continuously, it grows on a region where the surface is not oxidized, improving the crystallinity of the current confinement layer and eliminating leakage current. Furthermore, SiO2
Because growth occurs without forming layers, S! 02 '14
This avoids the deposition of polycrystals on the active layer, improves yield, and eliminates the occurrence of scratches due to differences in expansion coefficients, which prevents dislocations from occurring within the active layer.
It also extends your lifespan.

[Example] Hereinafter, an example of the present invention will be described with reference to FIG.

First, n - Q a A S % plate 1 (carrier Iaf
311 (IX1018Cm3) 17 on (100) surface
) Etching is performed using a phosphoric acid-based etching solution using the <011> direction photoresist as a mask, and
Form a stripe (ridge) 12 (Fig. 1(a)
). At this time, etching is performed to a depth of 2.5 μm or more from the substrate surface.

Next, this n-G a A S B board 1 is MOCVDH
The same epitaxial growth as described above is carried out to form an n-cladding layer 2 on the square stripe 12.
p-active layer 3, p-cladding layer 4 and 012991 layer 5
are formed sequentially. Here, these ")-cladding layer 2,
The active layer 3, the p-cladding M4, and the 012991 layer 5 have a substantially isosceles triangular cross section (FIG. 1(b)).

This triangular surface n (always 54.7° with the core aAs substrate 1)
For example, in order to make the active layer width 3 3 μm, the width of the meza stripe 120 should be 5 μm. Further, although the epitaxial layer grows in areas other than the mesus 1 to live 12, there is no problem because a high resistance layer is grown on the contact layer in the next epitaxial growth.

The growth of GaAS was terminated at a predetermined distance above the p-active layer 3 on the soristripe 12, and the growth of GaAS
Avoid growing the current confinement layer 6 (FIG. 1(C)).

Next, the epitaxial 1-sittle substrate is taken out from the MOCVD apparatus, and etching is performed on the active region using a resist or the like as a mask to avoid exposing the 012991 layer 5 (FIG. 1(d)).

Thereafter, a commonly used wafer wrestling process for semiconductor laser devices is performed to complete the semiconductor laser device (FIG. 1(e)).

FIG. 2 shows the current-optical output characteristics of the embedded semiconductor radar device manufactured according to this example. It was confirmed that the oscillation threshold value was 10% lower than that of the buried type semiconductor SIA element manufactured in the conventional example in Figure 4 (example in Figure 3). It is thought that this is because the current density flowing through the active layer 3 increased due to the formation of .

In addition, the yield rate was investigated between the manufacturing method according to this embodiment and the manufacturing method according to the prior art shown in FIG.

Using this embodiment, a good product could be prototyped from the entire substrate, whereas in the conventional method, polycrystals adhered to some of the 8102 layers and 12, making it impossible to make a good product.

Furthermore, when we conducted a life test on the obtained good products, we found that
Compared to conventional manufacturing methods, the rate of non-defective products that can be continuously excavated for longer than the specified time has increased by more than 15%. This is 5ho2 and G
The number of dislocations caused by the difference in expansion coefficient from aAs is 5.
It is thought that this is because the RO2 layer 12 was not used, so it disappeared.

[Effect of the invention] By using the present invention, a buried semiconductor laser device can be manufactured without using selective growth, which reduces the number of man-hours and improves the crystallinity of the current confinement layer to improve the oscillation threshold. value is reduced. The lifespan is also extended because there is no stress caused by differences in thermal expansion coefficients.

[Brief explanation of drawings]

Figures 1 (a) to (0) are cross-sectional views showing the steps of the manufacturing method of the embedded semiconductor laser device according to the present invention, and Figure 2 (31) is a cross-sectional view showing the steps of the manufacturing method of the embedded semiconductor laser device according to the present invention. Output characteristic diagram, Figure 3 is the conventional GaAS-A I GaA
4(a) to 4(d) are cross-sectional views showing the process of manufacturing the example shown in FIG. 3. FIGS. 1... n-G, a A 5th base plate, 2... cladding layer, 3... p active layer, 4... p cladding layer, 5...
・・p] Ntaku 1-M, 6... Current constriction M, 7...
High resistance AlGaAs1ffl, 12-3.102 Layer] Figure (Part 1) Section (Part 2) Current (mA) Part 2)

Claims (1)

[Claims] A step of forming a mesa stripe in the <011> direction on the (100) plane of the GaAs substrate, and
_xAs first cladding layer, Al_yGa_1_-_yA
s active layer, Al_xGa_1_-_xAs second cladding layer, and GaAs contact layer on the mesa stripe; burying the active layer with a high-resistance Al_zGa_1_-_zAs layer (where x≧z>y); 1. A method for manufacturing a buried semiconductor laser device, comprising the step of growing a current limiting layer on Al_zGa_1_-_zAs.