JPH05206566A - Manufacture of semiconductor laser element - Google Patents

Abstract

PURPOSE:To enable a semiconductor laser element to be doped with an optimal amount of dopant and formed optimal in profile so as to be of high performance by a method wherein the ratio of As4 molecule to group III atom flux is controlled, and Si is controlled in polarity. CONSTITUTION:A P-GaAS buffer layer 2, a P-AlGaAs clad layer 3, a GRIN- AlGaAs layer 4, a GaAs single quantum well active layer 5, and a GRIN-AlGaAs layer 6 are laminated on a P-GaAs (100) substrate 1. At this point, the ratio of AS4 molecule to group III atom flux is set to 1 or so, and Si is used as dopant, whereby a laminate is of P-type conductivity. Then, the ratio of As4 molecule to group III molecule flux is set to over 2, Si is made to serve as dopant, an N-AlGaAs clad layer 7 and an N-GaAs contact layer 8 are made to grow. By this setup, a semiconductor laser element, which oscillates in a basic transverse mode up to a high output power can be realized.

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 which greatly contributes to high performance of a compound semiconductor optical device.

[0002]

2. Description of the Related Art Conventionally, as a semiconductor laser device of this type, for example, See Harder et al., “Electronics Letter 1986, Vol. 22, No. 20, 1081 to 108.
Page 2 “High-power ridge waveguide AlGaAs GRI
N-SCH Laser Diode "[C. Harder
et al. "Electronics Lette
rs "25th September 1986 v
ol. 22 No. 20, page 1081-10
82 "High power ridge-wave
guide AlGaAs GRIN-SCH las
er diode ”].

FIG. 2 is a sectional view of such a conventional semiconductor laser device. In the figure, 21 is a Ge-Au-Ni layer, 22 is an n-GaAs substrate, 23 is a buffer layer, and 24 is n-Al.
The GaAs clad layer 25 is n-AlGaAs whose refractive index is graded by continuously changing the composition of aluminum.
-GRIN layer, 26 is a single quantum well active layer, 27 is p-
An AlGaAs-GRIN layer, 28 is a p-AlGaAs cladding layer, 29 is SiO ₂ , 30 is a p-GaAs contact layer, and 31 is a Ti-Pt-Au layer.

As shown in this figure, in this type of semiconductor laser device, buffer layers 23, n are formed on an n-type GaAs substrate 22 by a molecular beam epitaxial (MBE) method.
-AlGaAs cladding layer 24, n-AlGa having a graded refractive index by continuously changing the composition of aluminum
As-GRIN layer 25, GaAs single quantum well active layer 2
6, p-AlGaAs-GRIN layer 27, p-AlGa
A laser structure composed of the As clad layer 28 and the p-GaAs contact layer 30 is grown, and a ridge structure is formed by removing the p-AlGaAs clad layer 28 partway through chemical etching or dry etching to form a ridge structure and a portion other than the ridge. By confining the effective refractive index between and, the light is confined and the region other than the ridge portion is covered with the insulating film (SiO ₂ ) 29 to confine the current.

[0005]

However, since Be is used as the p-type dopant in the above-described method for manufacturing a semiconductor laser device, Be is not grown during growth at the optimum growth temperature of the AlGaAs cladding layer 28. Since it is difficult to control the anomalous diffusion of p, the optimum p-type doping amount and profile cannot be formed, which is an obstacle to improvement of device characteristics and yield.

SUMMARY OF THE INVENTION It is an object of the present invention to eliminate the above problems and provide a method of manufacturing a high performance semiconductor laser device using the MBE method.

[0007]

To achieve the above object, the present invention provides a method for manufacturing a semiconductor laser device,
In the molecular beam epitaxial growth method, GaAs (31
1) Using an A-plane substrate, Si having a small diffusion coefficient during growth as a p-type and n-type dopant, and using As ₄ molecules and III
In addition to controlling the group atom flux ratio, the polarity of Si is controlled to form the optimum doping amount and profile.

[0008]

According to the present invention, as described above, GaAs (3
11) On the A substrate, only Si having a small diffusion coefficient during growth is used as a dopant, and by utilizing the property that Si becomes p-type or n-type depending on the change in As pressure, the optimum doping amount and A semiconductor laser device having a profile can be obtained.

[0009]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a sectional view of a semiconductor laser device manufacturing process showing an embodiment of the present invention. First, as shown in FIG. 1A, MBE is formed on a p-GaAs (100) substrate 1.
P-GaAs buffer layer 2 (about 0.5 μm), p-AlGaAs cladding layer 3 (about 1.5 μm), undoped GRIN-AlGaAs layer 4, and undoped GaAs single quantum well active layer 5 (0. 01μ
m)), and an undoped GRIN-AlGaAs layer 6 is laminated. At this time, a group III atomic flux ratio of As ₄ molecules is set to about 1 and Si is used as a dopant to obtain p-type conductivity.

Then, the ratio of the As ₄ molecule to the group III atomic flux is set to 2 or more, Si is used as a dopant, and n-AlG is used.
aAs clad layer 7 (about 1.5 μm), n-GaAs
The contact layer 8 (about 0.5 μm) is grown. AlG
Optimum growth temperature of aAs clad layers 3 and 7 (700 to 7
Since Si does not cause abnormal diffusion during growth even at 50 ° C.), it is possible to form a good pin structure using the undoped GaAs single quantum well active layer 5 as an insulating layer, thereby reducing the threshold current and improving efficiency. Furthermore, since the p-type doping amount can be increased, heat generation at the time of high current injection can be reduced.

Next, as shown in FIG. 1 (b), after applying a resist layer 9, a usual lithographic technique is used,
A stripe having a width of about 3 μm is formed in the (0-11) direction. By using the resist layer 9 as a mask, chemical etching or dry etching is performed to form a ridge structure that is partially removed from the n-AlGaAs cladding layer, and an effective refractive index difference is provided between the ridge portion and the portion other than the ridge. Allow light to be trapped in the basic transverse mode.

Next, as shown in FIG. 1C, the ridge portion is filled with the polyimide layer 10 to confine the current. Further, the n-side electrode 11 is formed and the p-side electrode 12 is formed on the back surface. Further, the laser end face is formed by dry etching or cleavage. In the above description, the case where the p-GaAs (311) A substrate is used has been described, but a similar structure has the same structure as n-GaAs (3).
11) It can also be formed by using the A substrate.

The present invention is not limited to the above-mentioned embodiments, but various modifications can be made within the scope of the present invention, and these modifications are not excluded from the scope of the present invention.

[0014]

As described above in detail, according to the present invention, a GaAs (311) A plane substrate is used and AlGa
Even at the optimum growth temperature of As (700 to 750 ° C), Si with a small diffusion coefficient during growth is used, and As ₄ molecules and II
Since the group I atomic flux ratio can be controlled, the Si polarity can be controlled, and the doping region and the p-type doping amount can be increased, it is possible to easily realize a semiconductor laser device that oscillates in the fundamental transverse mode up to a high output.

The semiconductor laser device obtained by the present invention can be applied to a wide range of fields such as ultra-high-speed optical information processing and communication.

[Brief description of drawings]

FIG. 1 is a sectional view of a manufacturing process of a semiconductor laser device showing an embodiment of the present invention.

FIG. 2 is a sectional view of a conventional semiconductor laser device.

[Explanation of symbols]

 1 p-GaAs (100) substrate 2 p-GaAs buffer layer 3 p-AlGaAs cladding layer 4 undoped GRIN-AlGaAs layer 5 undoped GaAs single quantum well active layer 6 undoped GRIN-AlGaAs layer 7 n-AlGaAs cladding layer 8 n-GaAs contact layer 9 Resist layer 10 Polyimide layer 11 n-side electrode 12 p-side electrode

Claims (1)

[Claims] 1. In (a) a molecular beam epitaxial growth method, a GaAs (311) A-plane substrate is used, and Si having a small diffusion coefficient during growth is used as a p-type and an n-type dopant. (B) As ₄ molecules and III A method for manufacturing a semiconductor laser device, which comprises controlling an atomic flux ratio of a group and a polarity of Si to form an optimum doping amount and profile.