JPS63178574A - Manufacture of semiconductor laser device - Google Patents

Abstract

PURPOSE:To obtain a good regrown crystal while obtaining desired stripe width and thickness by using thermal sulfuric acid for forming a salient part of a clad layer. CONSTITUTION:After growing an n-GaAs buffer layer 2, an n-InGaP buffer layer 3, an n-InGaAlP clad layer, an InGaP active layer 5 and the first p- InGaAlP clad layer 13 on an n-GaAs semiconductor substrate 1, a p-InGaP layer 14, the second p-InGaAlP clad layer 15 and a p-GaAs ohmic contact layer 7 are formed. Then, a striped mesa is formed by etching a layer 7 with a mask of SiO2 8. Further, etching is performed down to the p-InGaP layer 14 by using thermal sulfuric acid so as to form the striped mesa having desired width and thickness. Next, n-GaAs 10 can be excellently buried with SiO28 as the mask to finish it by forming electrodes 11 and 12.

Description

[Detailed description of the invention] [Object of the invention] (Industrial application field)
The present invention relates to an lP-based semiconductor laser device, and particularly to a method for manufacturing a semiconductor laser device using a chemical vapor deposition method (hereinafter abbreviated as MOCVD method) using an organic metal.

(Conventional technology) In recent years, with the improvement of crystal growth technology of MOCVD method, He
-InGa provides oscillation wavelength comparable to that of No laser
Semiconductor lasers using AlP compound semiconductors are beginning to be manufactured (NIKKEI MICRODE
VICES November 1985 issue).

By the way, when these semiconductor lasers are used as light sources for video discs and laser printers, which have been attracting attention in recent years, there are problems that must be solved. That is, in addition to a structure that confines optical energy and injected current to a specific region to minimize optical loss and wasteful recombination.

Since it is necessary to narrow down the light to a minute spot on the order of 1 um, parallel light is confined in the active layer of the semiconductor laser. In other words, it was necessary to control the transverse mode.

Therefore, the present inventors fabricated a ridge-embedded laser as a laser structure that satisfies these conditions and confirmed that it oscillates in the fundamental transverse mode [33rd Applied Physics Association Lecture Proceedings 4Pk - k-14P-173)
.

First, Figure 1 shows a schematic cross section of this ridge-embedded laser.
d, and its structure and manufacturing method will be briefly explained using FIGS. 2abcd. This ridge-embedded laser has an n-GaAs buffer layer (■), an n-InGaP buffer layer (■), an n-In
GaAlP cladding layer), InGaP active layer 0, p-
After sequentially forming an InGaAlP cladding layer 0 and a p-GaAs ohmic contact layer (2), the p-GaAs ohmic contact layer was etched using an SH etching solution (mixture of 8 sulfuric acid + 1 hydrogen peroxide solution + 1 water) using the 5in2 mask as a mask. A striped mesa is formed, and then selective etching is performed using hot sulfuric acid as a mask to remove p-
The InGaAlP cladding is etched halfway, leaving the p-InGaAlP cladding layer with a thickness h, and then etching the p-GaAlP cladding layer.
Selective growth using low-pressure MOCVD method using 5ins@ as a selective growth mask to form a striped mesa 0 containing an As ohmic contact layer (Proceedings of the 2nd Crystal Engineering Symposium, Crystal Engineering Subcommittee of Japan Society of Applied Physics) (pH (1985)), and zero-order SiO□ filled with n-GaAs (10) except for the masked part.
After removing the mask, p-type l! Pole (11) and n-type electrode (12
) to form and complete. By the way, the laser with this structure has the width of the striped mesa and p(nGa
Since the characteristics vary greatly depending on the thickness h of the AIP cladding layer, it is important in the process to accurately control the width and thickness h of this mesa. In addition, growing the n-GaAs layer with good crystallinity during selective growth is also effective in suppressing the reactive current flowing through the n-GaAsN and allowing the current to flow efficiently only in the striped mesa. This is also important for efficiently dissipating heat from the inside. However, in the conventional manufacturing method, p
- The thickness h of the InGaAlP cladding layer was controlled by the etching time, so it was very difficult to control it. When the thickness h is controlled by time, even though the desired thickness h has already been obtained in some locations on the wafer, the desired thickness has not yet been reached in other locations. In addition, after etching the p-InGaAlP cladding layer, it is filled with n-GaAs by selective filling growth using the low-pressure MOCVD method.
Since it is a layer containing nGaAlP, that is, A1, oxidation occurs and there is a problem in that the growth of n-GaAs (10) thereon is not successful.

(Problems to be Solved by the Invention) As mentioned above, it is necessary to manufacture the stripe width and h with high precision, and to form a good n-GaAs layer on the crystal surface on both sides of the ridge after etching. It was necessary to form.

The present invention has been made to solve these problems, and it is possible to manufacture the stripe width and h with high precision.
In addition, the present invention provides an excellent method for manufacturing a semiconductor laser, which makes it possible to form a good n-GaAs layer on the surface after etching.

[Structure of the invention]

(Means for Solving the Problem) As a means of etching the above-mentioned stripe width and h with high precision, an InGaP layer is provided between the P-InGaAlP cladding layer in which a ridge is formed in advance, and a selective etching solution for InGaAlp and InGaP is used. Etch with sulfuric acid.

(Function) By providing an InGaP layer between the p-InGaA1p cladding layers, a desired stripe width and h can be obtained, and a regrown crystal with good crystallinity can be obtained.

(Example) An example according to the present invention will be specifically described below using FIG. 1abcd.

FIG. 1(d) shows a schematic structure of a semiconductor laser device according to an embodiment of the present invention.
) and (d) are diagrams showing the manufacturing process of the above laser. First I! ! As shown in (a), one layer of n-GaAs buffer (■) and an n-I
nGaP buffer layer 1, n-InGaAlP cladding layer), InGaP active layer 0, first p-InGaAl
After growing the P cladding layer (13), a p-InGap (14) of about 0.01. , then the second p by the desired value i.e. h
-InGaAlP cladding layer (15) is made of p-GaAs
Ohmic contact layer 0 was sequentially formed, and then Si
The aAs ohmic contact layer is etched using an SH etching solution (a mixture of 8 sulfuric acid + 1 hydrogen peroxide solution + 1 water) using O□■ as a p- mask to form a striped mesa, and then InGaP, GaAs, and InGaAL are etched.
Etching was carried out using hot sulfuric acid having excellent selectivity with P until reaching the p-InGaP layer serving as an etching stopper and an easy-to-grow layer, thereby forming a striped mesa.

At this time, hot sulfuric acid does not etch InGaP, so I
Etching could be performed until the nGaP layer was exposed over the entire wafer, and the desired h could be obtained. Next, using this Sin as a mask for selective growth, low-pressure MO
A certain portion of the 5in2 mask is filled with n-GaAs (10) by selective growth using the CVD method. At this time I
Unlike InGaAlP, nGaP does not contain A1, so even if it is exposed to the atmosphere after etching, there is little oxidation on the surface and there is no problem with regrowth on it, and even in this example, it is much better than when the surface is InGaAlP. An improvement in crystallinity was observed. Next, after removing the 5in2 mask, a p-type electrode (11) and an n-type electrode (12) were formed to complete the process.

According to this example, the uniformity of h due to etching was significantly improved, and the surface condition and crystallinity after regrowth were also significantly improved, resulting in improved properties. In addition, the P-InGaP layer as an etching stopper and an easy-to-grow layer is about 0.01
Since it is as thin as m, it does not have any effect on the mode of light guided to the ridge.

〔Effect of the invention〕

As described above, according to the present invention, the uniformity of h is significantly improved, and the surface condition and crystallinity after regrowth are also significantly improved, resulting in improved properties.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the structure and manufacturing method of a ridge-embedded laser according to the present invention, and FIG. 2 is a diagram showing a conventional example. 1... GaAs substrate 2... n-GaAs buffer layer 3... n (n-GaP buffer layer 4... n-InGaAlP cladding layer 5... InG
aP active layer 6-p-InGaAlP cladding layer 7... p-GaAs ohmic contact layer 8...
Sun, mask 9...stripe mesa (ridge) 10-n-GaAs 11-p-type electrode 1
2...n-type electrode 13...first InGaAlP cladding layer 14...
InGaP layer 15 as a stopper and easy-to-grow layer
...InGa as second stopper and easy-to-grow layer
P layer agent Patent attorney Nori Chika Yudo Kikuo Takehana Figure 1

Claims (1)

[Claims] InGaAl of the first conductivity type is formed on the semiconductor substrate of the first conductivity type.
After sequentially forming the InAlP cladding layer and the ohmic contact layer, the P cladding layer, the active layer, and the second conductivity type InGaAlP are formed.
In a method for manufacturing a semiconductor laser device, selective etching is performed halfway through a P cladding layer to form a convex stripe, and then the convex stripe portion is removed and a current blocking layer is formed. 1. A method for manufacturing a semiconductor laser device, characterized in that hot sulfuric acid is used to form the portion.