JPH0423379A - Semiconductor laser and manufacture thereof - Google Patents

Abstract

PURPOSE:To improve the surge breakdown strength of a semiconductor laser by a method wherein a semiconductor electrode layer, which is formed so as to reach a plane identical with the upper part of a mesa part and has the same conductivity type as that of a second clad layer, is provided on a semiconductor current constricting layer, which has a conductivity type reverse to that of the second clad layer and has a height not exceeding the height of the mesa part. CONSTITUTION:A P-type second Ga0.5Al0.5As clad layer 4 is etched using a mesa etching mask consisting of an insulating film 6 in such a way that the central part of the layer 4 is formed into a striped mesa type. At this time, one part of the layer 4 is left and an active layer 3 is prevented from being exposed to the atmosphere. After this, an N-type GaAs semiconductor current constricting layer 8 is selectively crystal-grown by an MOVPE method as the insulating film mask is left. The film thickness of this layer 8 is formed so as not to exceed the height of a mesa part. Subsequently, a P-type GaAs semiconductor electrode layer 9 is selectively crystal- grown on the layer 8 by an MOVPE method. The layer 9 is grown until the sum total of the film thickness of the layers 9 and 8 becomes a film thickness to reach a plane just identical with the upper part of the mesa part, the film 6 is removed with a phosphoric acid and a semiconductor laser is completed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a semiconductor laser device used in optical disk memories, etc., and a method for manufacturing the same.

2. Description of the Related Art Semiconductor laser devices are used as light sources for terminal devices of optical disk memories, and various striped structures have been proposed. Figure 3 shows one example of this, which has a mesa-shaped cladding layer (Japanese Patent Application Laid-Open No. 1-232784
(see Japanese Patent Application Laid-Open No. 1209779).

In the figure, 21 is a semiconductor substrate, 22 is a first cladding layer, 23 is an active layer, 24 is a mesa-shaped second cladding layer, 2
5 is a semiconductor electrode layer formed on the upper part of the mesa, 26 is a semiconductor current confinement layer, 27 is a semiconductor cap layer, and 28 and 29 are electrodes.

The performances required of a semiconductor laser device as a practical light source for compact discs (CDs), optical files, etc. are maximum optical output at one oscillation wavelength, astigmatism, single mode, low operating current, and low operating voltage. In addition to the electro-optical properties of
One example is reliability in an industrial sense. One item of reliability is electrostatic breakdown voltage. What is shown in Fig. 4 is an example of an electrostatic breakdown voltage measurement test using a human body charging model specified by the Electronic Machinery Industries Association (EIAJ) standard (ETAJ-C method) (EIAJ rc-121-1981E
S D).

The point at which the oscillation threshold current of a semiconductor laser device changes is defined as the surge withstand voltage. The conventional semiconductor laser device shown in Fig. 3 has a discharge capacity (Cp) of 200 pF and a discharge resistance (Rri).
When performing a destructive test with 0Ω and applied voltage (~') as parameters, the surge withstand voltage is 120■ when a surge current flows in the forward direction of the semiconductor laser device, and the surge current flows in the reverse direction of the semiconductor laser device. When this was done, the surge withstand voltage was 800V. At EIAJ, the amount of charge on the human body was considered to be 150V in this model, and a semiconductor laser device with excellent surge resistance was desired. In FIG. 4, reference numeral 30 denotes a measurement stand into which a semiconductor laser device is inserted and connected.

Problems to be Solved by the Invention Since such a conventional semiconductor laser device has a structure in which the semiconductor current confinement layer has the same height as the upper part of the mesa part,
There was a limit to increasing the surge pressure.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a semiconductor laser device having a high breakdown voltage and a method for manufacturing the same.

Means for Solving the Problems In order to achieve the above-mentioned objects, the present invention provides a first semiconductor substrate of the same conductivity type as the semiconductor substrate formed on a semiconductor substrate of ~ conductivity type.
a cladding layer, an active layer formed on the first cladding layer, and a second cladding layer of a conductivity type opposite to that of the first cladding layer formed on the active layer and having a striped mesa shape. a second cladding layer, a semiconductor electrode layer of the same conductivity type as the second cladding layer formed above the mesa portion of the second cladding layer, and a second cladding layer excluding the striped mesa portion in the center. A semiconductor current confinement layer having a conductivity type opposite to that of the second cladding layer formed above and not exceeding the height of the mesa portion of the second cladding layer; It has a configuration including a second cladding layer formed to be flat and a semiconductor electrode layer of the same conductivity type.

Effect of the present invention With the above-described configuration, it is thought that the thickness of the semiconductor current confinement layer is set to form a bypass against the inflow of surge current, and it is presumed that the surge withstand voltage is improved. Although the exact mechanism is not clear, this value was found through various experiments within a range that does not interfere with the operation of normal semiconductor laser devices.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to FIGS. 1 and 2.

First, as shown in FIG. 1 (al), on a semiconductor substrate 1 (100 μm) made of n-type GaAs,
sAl. The first cladding layer 2 made of sAs has a thickness of 1.0μ.
m grow.

Furthermore, undoped G ao, ssA I 0. +
The active layer 3 made of 2A S is 0.09 μm thick and has a p-type GaO layer.
,sAj! The second cladding layer 4 made of o5As is 1.
0 μm1 and a semiconductor electrode layer 5 made of a p-type GaAs layer.
is grown to a thickness of 0.2 μm. At this time, crystal growth is carried out by using group I elements and p-type dopant Zn with alkyl metal compounds (trimethylaluminum, trimethylgallium, diethylindium), group V elements and n-type dopant with hydride (
The process was carried out using a conventional metal organic vapor phase epitaxy method (MOV PE). The pressure was atmospheric pressure, and the growth temperature was 760°C. After this, Figure 1 (b
As shown in FIG.
An insulating film 6 (SiN) was formed by 1000 people. Furthermore, the photoresist pattern 7 shown in FIG. 1(C) is processed into a stripe shape using a normal photolithography technique.

Next, as shown in FIG. 1 (id), using this photoresist pattern 7 as a mask, the insulating film 6 is etched with a buffered hydrofluoric acid solution to form a mesa etching mask, and then the photoresist pattern 7 is removed. Next, using the mesa etching mask made of the insulating film 6, the second cladding layer 4 is etched with a mixed solution of sulfuric acid and hydrogen peroxide so that the central part becomes a striped mesa shape. At this time, a part of the second crat layer 4 is left to prevent the active layer 3 from being exposed to the atmosphere. Thereafter, as shown at te+ in FIG. 1, a semiconductor current confinement layer 8 made of n-GaAs is selectively crystal-grown using the MOVPE method while leaving the insulating film mask. The thickness of this semiconductor current confinement layer 8 should not exceed the height of the mesa portion. Subsequently, a semiconductor electrode layer 9 made of p-GaAs is placed on the semiconductor current confinement layer 8 by MOVP.
Crystals are selectively grown using the E method. The total thickness of the semiconductor electrode layer 9 and the semiconductor current confinement layer 8 is grown to a thickness that is exactly flush with the upper part of the mesa portion, and the insulating film 6 is removed with phosphoric acid heated to 100° C. to complete the semiconductor laser device. do. If the sum of the film thicknesses of the semiconductor electrode layer 9 and the semiconductor current confinement layer 8 does not grow to a thickness equal to or greater than that of the upper part of the mesa part, the heated phosphoric acid in the step of removing the insulating film 6 will cause the mesa-shaped The structure according to the present invention cannot be created because the etching may wrap around the upper end of the second cladding layer 4 and the second cladding layer 4 may be etched. Subsequently, as shown in FIG. 1 tf+, a semiconductor cap layer 10 made of p-GaAs is grown to a thickness of 2 μm on the semiconductor heavy F layers 5 and 9, and further, as shown in FIG. 1 fg+
As shown in FIG. 2, a p-side electrode 11 may be deposited on the semiconductor cap layer 10 and an n-type electrode 12 may be deposited on the back surface of the semiconductor substrate 1, and then cleaved and scribed to form a semiconductor laser device.

FIG. 2 shows the relationship between the thickness of the semiconductor current confinement layer 8 and the forward surge breakdown voltage of a semiconductor laser device according to the present invention having the cross-sectional structure diagram of FIG. 1. At this time, EIAJ-
A breakdown test was conducted to measure electrostatic breakdown voltage using a human body charging model defined by method C, using a discharge capacity weight of 200 pF, a discharge resistance of 0 Ω, and an applied voltage as parameters. As is clear from the figure, the forward surge withstand voltage has a correlation with the film thickness of the semiconductor current confinement layer 8, and in order to exceed 150cm, which is considered as the amount of charge on the human body according to EIAJ, it is sufficient to have a thickness of 0.6 μm or less. I understand that. However, in actual semiconductor laser devices, the semiconductor current confinement layer 8 is thin (if it becomes too thin, it becomes impossible to constrict the current during operation. The limit of its thinness is determined by the operating current of each semiconductor laser device and Since it is specified by the output, it cannot be determined uniquely.

In this example, the crystal material is GaAj! Although As-based 2 is used, it can also be applied to other materials such as InGaAsP-based and InGaAsP-based.

Effects of the Invention As is clear from the above embodiments, according to the present invention, a first cladding layer formed on a semiconductor substrate of one conductivity type and having the same conductivity type as that of the conductor substrate; an active layer formed on the active layer; a second cladding layer formed on the active layer and having a conductivity type opposite to that of the first cladding layer having a striped mesa shape in the center; A semiconductor electrode layer of the same conductivity type as the second cladding layer formed above the mesa portion of the layer, and the second cladding layer formed on the second cladding layer excluding the striped mesa portion at the center. a semiconductor current confinement layer having a conductivity type opposite to that of the second cladding layer and not exceeding the height of the mesa portion of the second cladding layer; Since the structure includes a semiconductor electrode layer of the same conductivity type as the cladding layer, a semiconductor laser device with high surge withstand voltage can be provided.

[Brief explanation of the drawing]

FIG. 1 (al to (gl) is a process cross-sectional view of a semiconductor laser device according to an embodiment of the present invention, and FIG. 2 is a film thickness and forward surge breakdown voltage of a semiconductor current confinement layer in an embodiment of the present invention shown in FIG. 3 is a cross-sectional view of a conventional semiconductor laser device, and FIG. 4 is a circuit diagram showing a method for measuring electrostatic breakdown voltage using a human body charging model. 1... Semiconductor substrate, 2... First cladding layer, 3... Active layer, 4... Cladding layer of both cylinders 2, 5... Semiconductor electrode layer, 8...・・・
Semiconductor current confinement layer, 9... Semiconductor electrode layer. Name of agent Patent attorney Shigetaka Awano Figure 18

Claims (5)

[Claims] (1) A first cladding layer of the same conductivity type as the semiconductor substrate formed on a semiconductor substrate of one conductivity type, an active layer formed on the first cladding layer, and a first cladding layer formed on the active layer. a second cladding layer having a conductivity type opposite to that of the first cladding layer and having a striped mesa-shaped central portion; and the second cladding layer formed on the mesa portion of the second cladding layer. a semiconductor electrode layer having the same conductivity type as the semiconductor electrode layer, and a second cladding layer having a conductivity type opposite to that of the second cladding layer formed on the second cladding layer excluding the central striped mesa portion; a semiconductor current confinement layer that does not exceed the height of the mesa portion of the layer; and a semiconductor of the same conductivity type as the second cladding layer formed on the semiconductor current confinement layer so as to be flush with the upper part of the mesa portion. A semiconductor laser device having an electrode layer. (2) A semiconductor cap layer of the same conductivity type as the second cladding layer is formed on the semiconductor electrode layer formed on the mesa portion of the second cladding layer and the semiconductor electrode layer formed on the semiconductor current confinement layer. The semiconductor laser device according to claim (1). (3) The semiconductor laser device according to claim 1 or 2, wherein the semiconductor current confinement layer has a thickness of 0.6 μm or less. (4) forming a first cladding layer of the same conductivity type as the semiconductor substrate on a semiconductor substrate of one conductivity type;
forming an active layer on the cladding layer; forming a second cladding layer of a conductivity type opposite to that of the first cladding layer on the active layer; and forming an active layer on the second cladding layer. A step of forming a semiconductor electrode layer of the same conductivity type as the second cladding layer, a step of forming a striped insulating film on the semiconductor electrode layer, and a step of forming the semiconductor electrode layer using the striped insulating film as a mask. etching the second cladding layer to form a mesa shape; forming a semiconductor current confinement layer having a thickness not exceeding the height of the mesa portion of the second cladding layer; A method for manufacturing a semiconductor laser device, comprising the steps of forming a semiconductor electrode layer of the same conductivity type as the layer, and removing the striped insulating film. (5) After the step of removing the striped insulating film, a second clad layer is formed on the semiconductor electrode layer formed on the mesa portion of the second clad layer and the semiconductor electrode layer formed on the semiconductor current confinement layer. 5. The method of manufacturing a semiconductor laser device according to claim 4, further comprising the step of forming a semiconductor cap layer of the same conductivity type as the semiconductor laser device.