JPH06216461A - Manufacture of semiconductor laser element - Google Patents

Abstract

PURPOSE:To provide a laser capable of operating in multispectral mode with a low-level operating current. CONSTITUTION:When a stripe mesa part 8 is formed in a second clad layer 5, a thickness of the second clad layer 5 of the region where the mesa part 8 is not formed is made 0.3mum or less and a current interception layer 12a composed of an AlZGa1-ZAs layer 12a and a GaAs layer 12b is formed on the side plane of the mesa part 8, whereby the beam of lateral direction of the obtained semiconductor laser element is confined under the best condition and multispectral mode is achieved with a low-level operating current.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor laser device.

[0002]

2. Description of the Related Art In general, a semiconductor laser device is used as a light source for a compact disc, a video disc, etc., and therefore the structure of the device is designed so that light loss and wasteful recombination are minimized. It is necessary to confine energy and injected current, and further to confine light to a minute spot on the order of 1 μm, and to confine light in a direction parallel to the active layer of the device, that is, a structure capable of controlling transverse mode oscillation. In fact, a ridge-embedded semiconductor laser device that satisfies these structural conditions is known.

2 (a) to 2 (d) show main manufacturing steps of the ridge-embedded semiconductor laser device and its device structure. First, on the n-type GaAs substrate 1, n-type AlG
A buffer layer 2 of aAs is formed, and n-type A is further formed on the buffer layer 2.
_{l X Ga 1-x As (} 0.3 <X <1) first cladding layer _{3, Al Y Ga 1-Y As} (0 <Y <0.2) active layer 4, p-type Al _X Ga ₁ After laminating the second cladding layer 5 of _-x As 5 and the ohmic contact layer 6 of p-type GaAs in this order, a SiO ₂ mask 7 is formed on a necessary portion of this laminated body [FIG. 2 (a)].

Next, using an SH etching solution which is a mixed aqueous solution of sulfuric acid and hydrogen peroxide, selective etching is performed so that the thickness h of the second cladding layer 5 is left to 0.3 μm. The strip-shaped mesa portion 8 including the contact layer 6 is formed on the second cladding layer 5 [FIG. 2 (b)]. Then, reduced pressure metalorganic using chemical vapor deposition (MOCVD), in contact with the side surfaces of the mesa portion 8, embedding the current blocking layer 9 made of n-type GaAs which is selectively grown by SiO ₂ mask 7 [2 ( c)].

Finally, the SiO ₂ mask 7 is removed, and the n-type electrode 10 and the p-type electrode 11 are formed on the upper and lower sides of this laminated body to obtain a ridge-embedded semiconductor laser device. [FIG.2 (d)]. In the process of manufacturing such a semiconductor laser device, it is of course possible to manufacture a device having a similar structure and having opposite conductivity types.

[0006]

However, the above manufacturing method has the following problems. That is, when the ridge-embedded semiconductor laser device is used in a compact disc or a video disc, the laser light spectrum mode is multi-mode to suppress the return light noise of the optical pickup, and the operating current for downsizing and power consumption saving. Is important. To meet these conditions, the active layer 4
A modest light confinement in the lateral direction is required. In order to make the laser light spectrum mode of the ridge-embedded semiconductor laser device multi-mode, the thickness h of the second cladding layer 5 is set to 0.5 μm or more, and the GaAs layer having a large refractive index and absorbing light is activated. By keeping it away from layer 4, the lateral light confinement must be weakened. However, if the thickness h of the second cladding layer 5 is increased,
The confinement of the injection current becomes weak, and the operating current increases due to the generation of reactive current. Therefore, it is desired to suppress the increase of the operating current as much as possible and to make the laser light spectrum mode multi-mode.

The present invention has been made in view of the above points, and an object thereof is to provide a light blocking layer with a two-layer structure of an Al _Z Ga _{1 -Z} As layer and a GaAs layer. Another object of the present invention is to provide a method for manufacturing a semiconductor laser device capable of confining the laser light to reduce the operating current and making the laser light spectrum mode multimode.

[0008]

In order to solve the above-mentioned problems, according to the method of the present invention, after forming a stripe-shaped mesa portion including a contact layer in the second cladding layer, conventionally, n-type GaAs is used.
The current blocking layer, which was formed independently, was composed of an Al _Z Ga _{1 -Z} As layer having a small refractive index and not absorbing light, and a Ga absorbing light.
It is formed by stacking with an As layer.

[0009]

The thickness of the region of the second clad layer where the mesa portion is not formed is 0.3 μm or less, the current confinement is strengthened to suppress the operating current, and the current blocking layer having a small refractive index is used for lateral light Can be weakened and the laser light spectral mode can be made multimode.

[0010]

EXAMPLES The present invention will be described below based on examples. 1 (a) to 1 (d) show the main manufacturing steps of a semiconductor laser device according to the method of the present invention, and the portions common to FIGS. 2 (a) to 2 (d) are represented by the same reference numerals. First, n-type GaAs
N-type AlGaAs buffer layer 2 is formed on a substrate 1 of, and n-type Al _X Ga _1-x As (0.3 <X <
1) First clad layer 3, Al _Y Ga _1-Y As (0 <Y
<0.2) active layer 4, p-type A with 0.9 μm thickness
After the second cladding layer 5 of l _x Ga _1-x As is grown by MOCVD in sequence, a p-type GaAs ohmic contact layer 6 having a thickness of 0.1 μm is further deposited thereon, and A SiO ₂ mask 7 is formed on a necessary portion on the laminated body [FIG. 1 (a)].

Next, the contact layer 6 and the second cladding layer 5 which are not covered with the SiO ₂ mask 7 are treated with an SH etching solution, and the thickness h of the second cladding layer 5 is reduced to 0.2 μm. Are selectively etched so as to leave the stripe-shaped mesa portion 8 including the contact layer 6 in the second cladding layer 5 [FIG. 1 (b)]. Next, decompression MOC
Using the VD method, SiO 2 is contacted with the side surface of the mesa portion 8.
N-type Al _Z Ga _1-Z A selectively grown by ₂ mask 7
0.3 μm of s (0 <Z <X) layer 12a and n-type GaA
0.7 μm of the s layer 12b is formed on the second cladding layer 5, and the current blocking layer 12 composed of these two layers is embedded [FIG. 1 (c)].

Finally, as in the case of FIG. 2D, SiO
_{2 The} mask 7 is removed, and the n-type electrodes 10 are formed above and below this laminated body.
By forming the p-type electrode 11 and the p-type electrode 11, a ridge-embedded semiconductor laser device can be obtained. [Figure 1
(D)]. As described above, the difference between the method of the present invention and the conventional method is that when the current blocking layer 12 is buried, the n-type Al layer is used instead of the n-type GaAs 9 alone layer [FIG. 2 (c)].
_{The Z} Ga _{1 -Z} As layer 12a and the n-type GaAs layer 12b have a two-layer structure.

[0013]

As described above, according to the present invention, the obtained semiconductor laser device has an n-type Al _Z which enhances current confinement.
The current blocking layer composed of two layers, a Ga _{1 -Z} As layer and an n-type GaAs layer formed on the Ga _{1 -Z} As layer and having an appropriate distance from the active layer, makes it possible to optimize the optical confinement, With a low operating current, the laser light spectrum mode can be multimode.

[Brief description of drawings]

FIG. 1 shows main manufacturing steps of a semiconductor laser device according to the method of the present invention, in which (a) is a laminated state of each semiconductor,
(B) is a schematic sectional view showing a state in which a mesa portion is formed, (c) is a state in which a current blocking layer is embedded, and (d) is a state in which upper and lower electrodes are attached.

FIG. 2 shows main manufacturing steps of a semiconductor laser device according to a conventional method, in which (a) is a laminated state of each semiconductor,
(B) is a schematic sectional view showing a state in which a mesa portion is formed, (c) is a state in which a current blocking layer is embedded, and (d) is a state in which upper and lower electrodes are attached.

[Explanation of symbols]

1 substrate 2 buffer layer 3 first clad layer 4 active layer 4 5 second clad layer 6 contact layer 7 mask 8 mesa portion 9 current blocking layer 10 n-type electrode 10 11 p-type electrode 11 12 current blocking layer 12a Al _Z Ga _{1 -Z} As layer 12b GaAs layer

Claims (2)

[Claims] 1. A first conductivity type Al _X Ga _{1- x} As (0.3 <X <1) first cladding layer, Al _Y Ga _1-Y As on one main surface of a first conductivity type semiconductor substrate. (0 <Y <0.2) active layer, second conductivity type Al _X Ga _1-x As second cladding layer,
After sequentially stacking a second conductivity type GaAs ohmic contact layer, a striped mesa portion including the second cladding layer and the ohmic contact layer is formed by selective etching, and the first conductivity type current blocking is formed on the side surface of the mesa portion. A method of manufacturing a semiconductor laser device in which a layer is embedded, wherein the first conductivity type Al _Z Ga _{1 -Z} A is used to fill the current blocking layer.
A method of manufacturing a semiconductor laser device, comprising forming a current blocking layer consisting of two layers in the order of an s (0 <Z <X) layer and a first conductivity type GaAs. 2. The method according to claim 1, wherein the thickness of the second cladding layer on the surface of the region where the linear mesa portion is not formed is 0.
A method of manufacturing a semiconductor laser device, wherein the thickness is 3 μm or less.