JPS63252496A - Semiconductor laser element - Google Patents

Abstract

PURPOSE:To constrict currents positively, and to improve electric thermal characteristics by forming a p-n-p-n junction layer occupying sections except the selective diffusion region of an impurity onto a second clad layer shaped onto an active layer. CONSTITUTION:An n-AlGaAs first clad layer 12 is formed onto the surface of an n-GaAs semiconductor substrate 11 through an epitaxial crystal growth method. An n-GaAs active layer 13, an n-AlGaAs second clad layer 14, a p- AlGaAs current blocking layer 15, an n-AlGaAs current blocking layer 16, an a p-GaAs cap layer 17 are shaped onto the surface of the clad layer 12 through the epitaxial crystal growth method in succession, a region 20 into which Zn is diffused selectively is formed, and electrodes 18, 19 are shaped.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a compound semiconductor laser device.

[Conventional technology]

In a refractive index waveguide semiconductor laser device, a waveguide with a refractive index distribution is formed in the active layer, and this serves as a waveguide region to determine a horizontal transverse mode. Conventionally, in the impurity control type in which a refractive index difference is created in the active layer by selective doping of impurities, as shown in FIG. 3, n-GaAs base [n-Ajl! GaAs cladding layer (2), n-GaAs
Active layer (3), n-AffiGaAs cladding layer (4)
,p-A/! GaAs current blocking layer (5), n-G
After sequentially forming aAs cap layers, the n-Aj layer from the cap layer (7) under the active layer (3) is formed by selective diffusion of impurities.
! By changing the region (7) that enters the GaAs cladding layer to p-type, zero emission is performed by carriers confined in the p'6M region of the active layer, and the horizontal transverse mode in the direction parallel to the active layer is It is controlled by the difference in refractive index caused by the difference in carrier concentration. In addition, current constriction is caused by n-Ga
This is done by using a reverse bias in the ρn heterojunction between the As layer (6) and the p-AlGaAs cap layer (5), or by depositing a SiOg film as an insulating film on the n-GaAs cap layer (6). Form, p SJ! StO in the area
□This is done by removing the film by selective etching and forming electrodes.

[Problems with conventional technology]

However, when performing current prongs with reverse bias at the n-p heterojunction, p-Aj! GaA
Drift current may be injected into the s-block layer (5), resulting in incomplete current confinement, and when high-temperature treatments such as diffusion are performed, the p-electrode material may enter the n-GaAs cap layer (6), resulting in - From the position of the p junction to the hetero interface n-
There is a problem that it migrates into the GaAs cap layer (6) and changes the current blocking properties. When current confinement is performed using a wA edge film, the insulating film may cause distortion or impair heat conduction. In addition, since a pn junction is formed across the entire interface of the p-diffusion region, the presence of defects in even a portion of the junction tends to cause current leakage.In either structure, the contact area of the p-electrode (8) is small; There is a problem that contact resistance increases.

The present invention has been made in view of the above points.
The purpose of this is to ensure current confinement and p! The object of the present invention is to provide a compound semiconductor laser device with excellent electrical and thermal characteristics by increasing the contact area of the poles and reducing the contact resistance.

[Means for solving problems]

In order to achieve the above object, the present invention includes a semiconductor substrate, a first cladding layer formed on the semiconductor substrate, an active layer formed on the first cladding layer, and a semiconductor substrate formed on the active layer. In a refractive index waveguide semiconductor laser device, the semiconductor laser device is composed of at least a second cladding layer formed on the second cladding layer, and has a difference in refractive index in the active layer due to selective diffusion of impurities. A semiconductor laser device is provided, characterized in that a p-n-p-n junction layer is formed that occupies a region other than the selective diffusion region of the semiconductor laser device.

[Operation] The operation of the present invention will be explained with reference to FIG. 1 showing one embodiment thereof.

On the n-GaAs active layer 03), an n-AlGaAs cladding 104), a p-Aj2GaAs block layer c,
-Aj! After epitaxially growing a GaAs block layer 0ω and a p-GaAs cap layer 07 in sequence, Zn is selectively diffused to form a Zn-diffusion region el. In this structure, except for the p region of the Zn-diffusion region [phase], p
- n-p-n thyristor structure is formed, and conventional n-p-n thyristor structure is formed.
Compared to pn) transistor structures, the current is more reliably confined to the Zn-diffusion region. Further, conventionally, current was injected only from the p diffusion region of the p-electrode, but in this embodiment, current is injected from the entire surface of the p-electrode, reducing the contact resistance of the p-electrode.

〔Example〕

The present invention will be described below based on embodiments shown in the drawings.

FIG. 1 is a cross-sectional view of essential parts showing one embodiment of the present invention, and is
On the aAs substrate OD, an n-AlGaAs cladding layer θ, an n-GaAs active layer 03), an n-AffiGaAs cladding layer 041. p-AI! , GaAs block layer Q
51. n-AlGaAs block NOω, p-GaAs
After epitaxially growing the cap layer 07),
A region QO in which Zn is selectively diffused is formed, and then p
Form electrode 00.

FIG. 2 is a cross-sectional view of main parts showing another embodiment of the present invention.
After sequentially epitaxially growing an n-GaAs cap layer (21) on the AfGaAs film C17 layer 0ω, Z
A region 0 is formed by selectively diffusing n, and p
- Form a GaAs cap layer 0η and a p-electrode 0[1). Even in this case, current is injected from the entire surface of the p-electrode 0a, reducing contact resistance.

Note that the present invention is based on the G a A s / A
The present invention is not limited to IGaAs-based compound semiconductors, and may also be implemented using, for example, InP/InGaAsP compound semiconductors. Furthermore, when implementing the present invention,
It is also possible to reverse the p-type and n-type in the above embodiments.

[Effects of the Invention] As explained above, according to the present invention, a p-n-p"n junction layer is formed on the second cladding layer formed on the active layer, occupying a region other than the selective diffusion region of impurities. This has the excellent effect of ensuring current confinement and reducing contact resistance of the P electrode.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a main part showing an embodiment of a semiconductor laser device according to the present invention, FIG. 2 is a cross-sectional view of a main part showing another embodiment of a semiconductor laser device according to the present invention, and FIG. FIG. 2 is a cross-sectional view of a main part of an example of a semiconductor laser device. 1.1l-n-GaAs substrate, 2.12=-n −
AlGaAs cladding layer, 3.13・=n-GaAs
Active layer, 4.14·n-A/l! GaAs cladding layer, 5.15-p-A1. GaAs layer 7 layer, 6
=-n-C; aAs cap layer, 7...p-diffusion region, 8.1B-p electrode, 9.19-n@pole,
16-n -AlGaAs block layer, 17-p
-GaAs chip layer, 20...Zn- diffusion region.

Claims (1)

[Claims] At least a semiconductor substrate, a first cladding layer formed on the semiconductor substrate, an active layer formed on the first cladding layer, and a second cladding layer formed on the active layer. In a refractive index guided semiconductor laser device having a difference in refractive index in the active layer due to selective diffusion of impurities, a p-n- A semiconductor laser device characterized by forming a pn junction layer.