JPH02168689A - Semiconductor laser device - Google Patents

Abstract

PURPOSE:To enable a low threshold and low current operation by bringing a semiconductor substrate to semi-insulating properties, forming the semiconductor substrate nearest to a striped groove of an epitaxial layer up to the rear and burying an opening section with an electrode metal. CONSTITUTION:A stripe window is shaped onto a semi-insulating GaAs substrate 11, and a hole is formed to an inverted V groove shape through etching by a reaction-rate controlling type etchant. A P-type GaAs epitaxial layer 12 and an N-type GaAs current blocking layer 2 are subjected to epitaxial growth continuously onto the semi-insulating GaAs substrate 11 to which the hole is formed. A stripe groove 7 is shaped, a P-type AlGaAs lower clad layer 3, a P-type GaAs active layer 4, an N-type AlGaAs upper clad layer 5 and an N-type GaAs contact layer 6 are formed while using the groove 7 as a substrate, and the semi-insulating GaAs substrate 11 is formed in specified thickness. Accordingly, a semiconductor laser device enabling a low threshold and low current operation and having high affiance can be acquired.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor laser device that oscillates with a low threshold current and can operate with a low current.

Semiconductor lasers that operate at low currents are required to be able to operate at low currents and be driven by dry batteries as CD lasers become smaller and more portable. It is necessary to think from the element structure, such as reducing the amount or increasing efficiency.

[Conventional technology]

FIG. 4 is a cross-sectional view of a conventional internal stripe type semiconductor laser device, in which 1 is a p-type GaAs substrate;
2 is an n-type GaAs current blocking layer, 3 is a p-type AjGaA
s lower cladding layer, 4 is p-type GaAs active layer, 5 is n-type A
6 is an n-type GaAs contact layer, 7 is a stripe groove (V groove) through which current flows for laser oscillation, and 8 and 9 are p-side and n-side electrodes, respectively.

FIGS. 5(a) to 5(d) are cross-sectional views at each stage for explaining the conventional method for manufacturing the semiconductor laser device, and the outline thereof is clear from the configuration of the device shown in FIG. , the outline will be explained without duplication.

First, an n-type GaAs current blocking layer 2 is grown (first epitaxial growth layer) on a p-type GaAs substrate 1 [FIG. 5(a)]. Next, stripe grooves 7 that will serve as current paths are formed in this epitaxial wafer using photolithography and etching techniques [FIG. 4(b)]. Furthermore, by multilayer epitaxial growth, p-type AjGaAs lower cladding layer 3p, p-type GaAs active layer 4. n-type AjGaAs
The upper cladding layer 5 and the n-type GaAs contact layer 6 are continuously grown (second epitaxial growth layer) [Fig. 5(c)
)). Next, using wafer process technology, polishing and t4
Complete the semiconductor laser device by forming the poles [Fig. 5 (
d)].

[Problem to be solved by the invention]

In conventional semiconductor laser devices, reactive current flows in areas other than the active region used for laser oscillation, resulting in low threshold and low II.
There was a problem that a semiconductor laser device capable of current operation could not be obtained. There are the following five main causes of reactive current generation.

■ Defective growth of n-type GaAs current blocking layer 2 ■ Crystal defect in n-type GaAs current blocking layer 2 ■ Pattern defect in photolithography during formation of V-groove 7 ■ Decrease in carrier concentration of n-type GaAg current blocking layer 2 ■ High voltage Tunneling phenomenon during application of voltage This invention was made to solve the above-mentioned conventional problems, and aims to provide a highly efficient semiconductor laser device that can operate with a low threshold and low current. .

[Means to solve the problem]

In the semiconductor laser device according to the present invention, the semiconductor substrate is semi-insulating, and the semiconductor substrate closest to the stripe groove is formed of an epitaxial layer until it reaches the back surface, or the semiconductor substrate closest to the internal stripe is formed to reach the back surface. A hole is opened up to the point where the hole is filled with electrode metal.

[Effect]

In the present invention, by making the portion through which the reactive current flows high in resistance, the current flows in a concentrated manner in the striped grooves.

〔Example〕

This invention will be explained below.

FIG. 1 is a sectional view of a semiconductor laser device showing an embodiment of the present invention. In FIG. 1, 11 is semi-insulating GaA
s substrate, 12 is a p-type GaAs epitaxial layer, 13 is a current bus region formed by this p-type GaAs epitaxial layer 12, and 2 to 9 have the same functions as the conventional semiconductor laser device shown in FIG. It is something you have.

FIGS. 2(a) to 2(,1) are cross-sectional views at each stage for explaining the method of manufacturing a semiconductor laser device according to the present invention.

First, a striped window (not shown) with a width of about 5 μm is formed using a resist mask on a semi-insulating GaAs substrate 11 by photolithography, and
Etching is performed using a reaction rate-limiting etching solution such as a H3OH/HzOz mixture to form a hole in the shape of an inverted V groove. Etching in this direction hardly progresses in the lateral <111> direction, but only in the depth direction <100> (Thus, the etching progresses deeper in the depth direction without increasing the width of the window. Figure 2(a)].The semi-insulating Ga with this hole formed
On the As substrate 11, by liquid phase epitaxial growth method,
p-type GaAS epitaxial layer 12 and n-type GaAs
The s-current blocking layer 2 is epitaxially grown continuously. In the liquid phase epitaxial growth method, the growth rate of the hole portion is fast and the growth rate of the flat part of the outermost surface is slow, so the p-type GaAs epitaxial layer 12 grows on a flat surface [Fig. 2(b) )]. Next, the window portion and the stripe groove forming portion are aligned with the cut 9 to form the stripe groove 7 [FIG. 2(C)]. Furthermore, using this as a substrate, p-type A
I G a As down rad layer 3y p-type GaAs
Active layer 4. an n-type AlGaAs upper cladding layer 5, and an n-type AlGaAs upper cladding layer 5;
After forming the type GaAs concrete layer 6, a semi-insulating GaAs substrate 11 is formed to a predetermined thickness through wafer process technology [FIG. 2(d)]0 The semiconductor laser device according to the present invention is clear from the above description. As shown, since the area other than the 5 μm window is semi-insulating, no reactive current flows to this area at all. For example, the threshold current of a conventional semiconductor laser device is approximately 30 mA, but according to the present invention, the threshold current is 15 mA.
This value is almost close to the theoretical value. That is, about half of 15
A reactive current of mA is eliminated, and a semiconductor laser device with a low threshold value and high efficiency can be obtained.

Furthermore, in the above embodiment, a method was described in which the semi-insulating GaAs substrate 11 was processed using a reaction rate-controlled etching solution.
RIE or sputtering may also be used.

FIGS. 3(a) to 3(g) are process cross-sectional views for explaining another method of manufacturing a semiconductor laser device of the present invention.

In this step, first, an inverted V-shaped groove is formed in the semi-insulating GaAS substrate 11 [FIG. 3(a)]. P-type or n-type AJ using this sea urchin as a substrate! The p-type GaAs epitaxial layer 1 is grown to fill the groove of the GaAs layer 14, and
2. Form a p-type GaAs current blocking layer 2 [third
Figure (b)]. After that, form a groove in the upper part of the window [3rd
Figure (C)]. Furthermore, using this as a substrate, p-type AlGaA
s lower cladding layer 3 p P-type GaAs active layer 4. n-type A
lGaAs upper cladding layer5. Then, each layer of the n-type GaAs contact layer 6 is successively grown [FIG. 3(d)]. Thereafter, in the wafer process step, the back surface is polished to approximately 85 μm [FIG. 3(e)]. P of the groove on the back side with HF
Only the type or n-type AjGaAs layer 14 is selectively etched away. HF is selective in etching GaAs and A#GaAs, etching only the AjGaAs layer, and etching GaAs! Since a is a liquid that does not etch at all, a structure as shown in FIG. 3(f) can be formed. Next, a metal 1 is placed as a p-side electrode in the hole 15 removed by selective etching.
6 into a buried via hole shape by plating or the like [Figure 3 (g)].

According to the above manufacturing method, not only can reactive currents that do not contribute to oscillation be prevented, but also electrodes can be formed very close to the active region, which is a heat source, resulting in good heat dissipation efficiency. Therefore, an ideal semiconductor laser device with low threshold current, low current operation, high oscillation efficiency, and good temperature characteristics can be obtained.

Furthermore, although all of the above embodiments have been explained using GaAs and AlGaAs systems as examples, the same applies to other IV and n-VI group compound semiconductors and their mixed crystals, such as InP and InGaAsP systems. Moreover, even when the conductivity types are reversed (p and n), exactly the same effect is exhibited.

〔Effect of the invention〕

As explained above, the present invention makes the semiconductor substrate semi-insulating, and either forms the semiconductor substrate closest to the stripe with an epitaxial layer until it reaches the back surface, or forms the semiconductor substrate closest to the internal stripe with an epitaxial layer. Since the hole is opened until it reaches the back surface and the hole is filled with electrode metal, the current flowing outside the groove can be halved, resulting in a semiconductor laser with low threshold current, low current operation, and high oscillation efficiency. There is an effect that the device can obtain.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a semiconductor laser device showing an embodiment of the present invention, FIG. 2 is a cross-sectional view showing the manufacturing process of the semiconductor laser device of FIG. 1, and FIG. 3 is a cross-sectional view of the semiconductor laser device of the present invention. 4 is a sectional view showing a conventional semiconductor laser device, and FIG. 5 is a sectional view showing a manufacturing process of the semiconductor laser device shown in FIG. 4. In the figure, 1 is a p-type GaAs substrate, 2 is an n-type GaAs substrate.
f4 flow blocking layer, 3 is p-type AI GaAs down rad layer, 4 is p-type GaAs active layer, 5 is n-type AlGaAs upper cladding layer, 6 is n-type GaAs contact layer, 7 is stripe Groove, 8 is pp1 electrode, 9 is n-side electrode, 11 is semi-insulating GaAs substrate, 12 is p-type GaAs
In the epitaxial layer, 13 is a current path region, 14 is a p-type or n-type At'GaAs layer, 15 is a hole, and 16 is a metal. Note that the same reference numerals in each figure indicate the same or corresponding parts. Agent Masuo Oiwa (2 others) Fig. Fig. Fig. 14: pt #7: I engineering n! ! AIGaAsJ diagram 1e) Metal

Claims (1)

[Claims] In an internal stripe type semiconductor laser device, the semiconductor substrate is semi-insulating, and the semiconductor substrate closest to the stripe groove is formed of an epitaxial layer until it reaches the back surface, or the semiconductor substrate closest to the internal stripe is formed to reach the back surface. 1. A semiconductor laser device characterized in that a hole is opened until the end of the hole and the hole is filled with an electrode metal.