JPH02288283A - Manufacture of semiconductor laser element - Google Patents

Abstract

PURPOSE:To obtain a semiconductor laser element equipped with an internal current constriction layer and refractive index distribution by applying gas source MBE method for formation of an active layer part and an internal current constriction layer and next using the MOCVD method. CONSTITUTION:For a silicon substrate 1, the one which has a face orientation of (100) and is off-angled about 3 deg. in the orientation of (011) is used, the after forming a film for buffer of CaAs by doing gas source MBE, an n-type AlCaAs clad layer 4, a CaAs active layer 4, and a p-type AlCaAs clad layer 5 are grown selectively in order on a stripe 12 by MOCVD method, whereupon the stripe is formed of an active layer part whose cross section being surrounded by face (111)B CaAs is triangle. Next, when a mask 2 is removed and gas source MBE is done again, a CaAs thin layer for buffer whose crystal orientation is rotated 90 deg. is formed, and when a p-type AlCaAs clad layer 6 is grown in two stages by MOCVD, the formation of the growth layer becomes the face surrounded by the face (100), the face (111)A CaAs and face (111)B GaAs. As a result, and internal current constriction layer and refractive index distribution can be made.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a semiconductor laser element, and more particularly to a method for manufacturing a semiconductor laser element formed by epitaxial growth of a lattice-mismatched system.

[Prior Art] Conventional light emitting elements, such as semiconductor lasers, are sometimes formed on silicon substrates mainly because of their advantages such as low cost, good mechanical strength, and good thermal conductivity. Semiconductor laser elements formed thereon have been limited to those having a gain waveguide structure without an internal confinement layer or artificial refractive index distribution. The reason for this is due to the technical aspect of crystal growth;
This is because a GaAs layer is grown in the same manner as described above, and therefore a highly efficient semiconductor laser device with a small beam divergence angle cannot be formed by incorporating the internal current confinement layer and refractive index distribution as described above.

In recent years, the technology of MBE (molecular beam epitaxial growth) has progressed, and progress has been made in the development of methods to self-annihilate antiphase boundaries in so-called lattice-mismatched epitaxial growth, such as growing a GaAs layer on a substrate. For example, there are those disclosed in the following documents.

Japanese Journal of Applied Physics
ppliedPhysics, 2G, [6F, (
1987-fli, ) (Sun), Japanese Society of Applied Physics, M. Kawabe, T. Ueda, “5elf
'-Anni-1+1latlon of' Antl
phase Border in GaAs on
5l (100) Grown by Mol'ecu
lar Beam Epitaxy, P.

L944-L94B,) However, there was no method of forming a semiconductor laser probe utilizing the novel properties of epitaxial growth as shown in the above-mentioned documents.

[Problems to be Solved by the Invention] In the conventional method for manufacturing a semiconductor laser device formed on a silicon substrate as described above, -
Since the structure consists of a double heterostructure of compound semiconductor layers, it is difficult to create an internal current confinement layer and refractive index distribution for carrier confinement.

This invention has been made to solve the above-mentioned problems, and aims to provide a method for manufacturing a semiconductor laser device having an internal current confinement layer and a refractive index distribution by applying the properties of selective growth on a silicon substrate. This is the purpose.

[Means for Solving the Problems] A method for manufacturing a semiconductor laser device according to the present invention includes (01
1) Silicone (10
0) After forming a mask on the substrate, heat treatment is performed on the substrate surface, and MBE growth is performed at an As adsorption temperature such that crystal growth occurs in the (100) direction but not in the (Ill) direction. After forming a thin GaAs layer,
Metal-organic chemical vapor deposition method (hereinafter abbreviated as 40CVD method)
An active layer of a compound semiconductor, which will become a light-emitting part, is formed by selective growth using the method.Then, the surface of the silicon substrate from which the mask is removed is heat-treated, and a thin film of a compound semiconductor whose crystal orientation is rotated by 90@ is deposited by the MBE method. A buffer layer is then formed, and a compound semiconductor layer is deposited again using the MOCVD method, thereby forming an internal current confinement layer as a buried layer so as to surround the active layer distribution.

[Function] In this invention, after forming a striped active layer portion on a substrate, an internal current confinement layer is buried and formed, but each portion is first formed by applying the property of changing crystal orientation by MBE method. Both are performed by a two-step growth method: first, and then growth using the selective growth characteristics of the MOCVD method.

That is, for the first active layer part, a silicon (100) substrate exposed by a mask is tilted about 3 degrees off-angle in the (011) direction, and the temperature of the silicon surface is set to 90 degrees.
After heat treatment at 0°C, the adsorption temperature of As in the first layer was set at 50°C.
After performing MBE at 0° C. or higher to form a thin layer of GaAs (buffer layer), the active layer portion is selectively grown using MOCVD to perform two-step growth of MBE and MOCVD.

In this way, from the experimental facts of the present inventors, in MOCVD low-pressure growth (IILIB GaAs surface has an extremely slow growth rate and hardly grows, 11111BGa
It has been discovered that an active layer portion with a triangular cross section surrounded by an As plane is formed by selective growth.

Next, after removing the mask, an internal current confinement layer is formed including the removed portion, but the adsorption temperature of the first layer of As after the surface heat treatment of the silicon substrate is set to 500°C or less to form a GaA layer.
After performing MBE growth of s, GaAs is grown by MOCVD in the same manner as the first two-step growth described above, and its orientation is rotated by 90°, forming the IIIA GaAs plane and the (10
0) Although it grows on the GaAs surface, IIIB GaA
Since they are not grown on the s-plane, the current blocking layer and cladding layer are formed in an inverted triangular shape opposite to the active layer portion, and a refractive index distribution is also formed at the same time. In addition, in the above, tl
The 111118 GaAs plane and the 111118 GaAs plane are defined as planes in which the first layer is Ga and As, respectively, in the 11111 plane.

[Example] FIGS. 1(a) and 1(b) are schematic explanatory diagrams showing a method for manufacturing a semiconductor laser device according to an example of the present invention.

FIG. 1(a) is a cross-sectional view up to the formation of the active layer portion, and FIG. 1(b) is a cross-sectional view showing the completed state of the semiconductor laser device. The manufacturing method and its state will be explained below in the order of FIGS. 1(a) and 1(b).

First, in FIG. 1(a), several thousand people formed a SI N film or a 310° film on an n-type silicon substrate 1 to be used as a mask 2 for selective growth using a normal vapor phase deposition (CVD) method. Thereafter, stripes 12 having a width of about 4 to 51 m are formed using a conventional lithography technique. The silicon substrate 1 used at this time has a (10G) plane orientation, and the (100) plane of the n-type silicon substrate 1 is (01
1) Use a device with an off-angle of about 3″ in the direction, and first introduce it into the MBE device and set it.

In this state, the heat treatment temperature of the surface of the silicon substrate 1 is set to 900℃.
.degree. C., and then MBE is performed with the adsorption temperature of the first layer of As at 500.degree. C. or higher to form a buffer thin film of GaAs (not shown) on the surface of the stripe I2.

Next, the silicon substrate 1 in this state is introduced into an MOCVD apparatus, and an n-type AJII GaAs cladding layer 3, a GaAs active layer 4, and a p-type^I GaAs cladding layer 5 are selectively grown on the stripe 12 in order by the MOCVD method. . Due to this selective growth, the stripes in the (011) direction form IIIB G as shown in FIG. 1(a).
An active layer portion is formed that is a grown layer surrounded by the aAs plane and has a triangular cross section. At this time, MOC
In the VD method, IIIBGa is generally grown during reduced pressure growth.
The As surface has an extremely slow growth rate and hardly grows.

At this time, as shown in FIG. 1(a), the n-type ANGaAs cladding layer 3 is about 1.5 IJmGaAs active layer 4 is about 1
000, p-type AN GaAs cladding layer 5 about 0.5
If it is about 1 Ja+, the width of the active layer will be about 1-. Each cladding layer has an impurity concentration of 5 x 10' (to) -
It should be about 3.

Next, the mask 2 of the substrate in the state shown in FIG.
When MBE is performed with the adsorption temperature of the first layer of As after the surface heat treatment of the silicon substrate 1 being 500° C. or lower, a thin GaAs layer for a buffer is formed in which the crystal orientation of the GaAs layer is rotated by 90″.Furthermore, The substrate in this state is introduced into an MOCVD device, and the p-type All GaAs cladding layer 6 is
When the second two-stage growth is performed by VD, the result is shown in Figure 1(b).
As shown in , the growth layer is formed on +1001 plane and III plane.
The surface is surrounded by the IA GaAs surface and the IIIB GaAs surface. At this time, growth occurs on the tllllA GaAs surface and the (100) GaAs surface, but IIIB
It does not grow on GaAs surfaces.

In this way, the p-type Aj?
On the GaAs cladding layer 6, an n-type A, 11-GaAs cladding layer (current blocking layer) 7, a p-type AN GaAs cladding layer 8, and a −-type GaAs cap layer 9 are successively grown.

At this time, the thickness of the p-type AllGaAs cladding layer 6 is such that the interface with the n-type AD GaAs current blocking layer 7 to be formed next is at the center of the active layer 4. Next, the n-type current blocking layer 7 is made to have a thickness of about 5,000 to 6,000 layers, and the p-type A
It should not cover the I GaAs cladding layer 5.

The p-type AN GaAs layer 8 to be formed next has a thickness of about 11JI.
11, and finally, a square GaAs cap layer 9 is formed. The cap layer may be around a few thousand people. In addition, the impurity concentration of the p-type AD GaAs cladding layer 8 is 5XlOcm,
The p+-Ga^S cap layer 9 is made to be .018cIn-3 or more. Finally, the p-type electrode lO1 and the n-type electrode 11
The formation of the basic structure of the semiconductor laser device up to the stage shown in FIG. 1(b) is completed.

As described above, the n-type AN GaAs cladding layer 3,
GaAs active layer 4, p-type AN GaAs cladding layer 5,
n-type^1) An internal current confinement layer is formed by the GaAs cladding layer 7, and the n-type AN GaAs cladding layer 3, p
A desired refractive index distribution is formed by the AN GaAs cladding layer 5, the n-type A (l GaAs cladding layer 7, and the p-type^f) GaAs cladding layer 8. With this configuration,
Because an internal current confinement layer was formed, which was not achieved in conventional semiconductor laser devices formed on silicon substrates,
Current confinement becomes easy, threshold current is small,
A laser beam with a small divergence angle is emitted from the end face of the active layer.

The manufacturing method of the present invention as described above uses GaAs.

A11l The material is not limited to GaAs-based semiconductor materials, but any material system may be used as long as it has selective growth characteristics on a silicon substrate and changes in crystal orientation due to surface treatment. Further, the polarity may be the same as the example described in the above example (opposite).

[Effects of the Invention] As described above, according to the present invention, a simple two-step process for forming a compound semiconductor layer on a silicon substrate takes advantage of the selective growth characteristics of the MOCVD method and the crystal orientation change characteristics of the MB2 method. By growing twice, it was possible to create an internal current confinement layer and a refractive index distribution on the silicon substrate without using techniques such as etching, so a semiconductor laser device with excellent light emission characteristics could be easily realized. . Furthermore, it has been suggested that by applying the manufacturing method of this invention to further refine and change the growth thickness of the active layer in selective growth, it is possible to realize a quantum wire laser of the quantum effect type, which is currently attracting attention. It has the effect of

[Brief explanation of drawings]

FIGS. 1(a) and 1(b) are schematic explanatory diagrams showing a method of manufacturing a semiconductor laser cable according to an embodiment of the present invention, and FIG. 1(a) is a sectional view showing the state of formation up to the active layer portion. , 1st
Figure (b) is a sectional view of a main part of the semiconductor laser cable in a completed state. In the figure, 1 is an n-type silicon substrate, 2 is a mask, 3 is an n-type Ap GaAs cladding layer, 4 is a GaAs active layer,
5 is p-type^(l GaAs cladding layer, 6 is p-type^ΩG
aAs cladding layer, 7 is n-type AΩGaAs cladding layer (
current blocking layer) 8 is a p-type AΩGaAs cladding layer;
9 is a p+ type GaAs cap layer, 1o is a p electrode (positive electrode)
, 11, n' is a pole (negative pole).゛・Nino (a) (b)

Claims (1)

[Claims] In a method for manufacturing a semiconductor laser device in which a compound semiconductor layer is formed on a silicon substrate by lattice-mismatched epitaxial growth, the silicon (
100) After forming a selective growth mask on the substrate and heat-treating the silicon surface, a crystal is grown in the opening of the mask so that the direction of crystal growth is in the (100) direction but not in the (111) direction. forming a GaAs thin layer by performing molecular beam epitaxial growth at a first layer As adsorption temperature, and performing organometallic vapor phase epitaxy on the region of the GaAs thin layer;
A cladding layer, an active layer, and a cladding layer are sequentially selectively grown to form an active layer portion, the mask is removed, and the silicon region is subjected to surface heat treatment, and then the direction of crystal growth is aligned with the direction of the molecular beam epitaxial growth. A thin layer of GaAs with a crystal orientation rotated by 90° is formed by molecular beam epitaxial growth at a temperature that changes by 90°, and compound semiconductor layers are successively deposited on the thin layer by organometallic vapor phase epitaxy. 1. A method of manufacturing a semiconductor laser device, which comprises growing and embedding an internal current confinement layer surrounding the active layer portion and forming a refractive index distribution.