JPH0821756B2 - Semiconductor laser manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a structure of a semiconductor laser in which deterioration of a cavity facet is prevented.

[Outline of Invention]

The present invention, in the semiconductor laser, the mixed crystal composition ratio in the vicinity of the end face of the active layer is set to a mixed crystal composition ratio having Eg larger than that of the active layer, which means that the thin film of the active layer is striped by ultraviolet rays during growth. By manufacturing by irradiating light, the band edge absorption of the laser oscillation light near the end face is eliminated and the injected carriers are not concentrated near the end face, so that the optical power is not concentrated near the end face and the end face deterioration is caused. A semiconductor laser which is prevented and has a long life and a large maximum output can be manufactured inexpensively with good reproducibility.

[Conventional technology]

The conventional window type double hetero semiconductor laser is the Applied Physics Letter.
Vol. 33 (1978) page 1011. FIG. 5 shows its main sectional view. (502) n-type GaA
(503) n-type Al _0.3 Ga _0.7 As cladding layer on the substrate,
(504) n-type Al _0.06 Ga _0.94 As active layer, (505) n-type
Clad layers of Al _0.3 Ga _0.7 As are sequentially laminated and (50
6) Form the SiO ₂ insulating layer. The SiO ₂ film is etched in stripes leaving the window region, and then the substrate is Zn.
It is vacuum-sealed in a quartz tube containing As ₂ etc. to diffuse Zn, and the layers of (505) and (504) are made P-type. After that, a P-type ohmic electrode (507) is formed on the upper part and an n-type ohmic electrode (501) is formed on the lower part. As a result, the active layer in the vicinity of the end face of the resonator is n-type, and the other is p-type to serve as a light emitting region. Since the n-type Al _0.06 Ga _0.94 As has a slightly larger Eg than the p-type, laser oscillation light is not absorbed in the vicinity of the end face, and the end face is prevented from being destroyed.

[Problems to be solved by the invention]

However, in the above-mentioned conventional technique, P-type AlGaAs and n-type AlGaAs
Since the difference in Eg is slight, a part of the laser oscillation light is absorbed, and it cannot be said that the effect is sufficiently increased in terms of increasing the optical output and extending the life. Furthermore, the diffusion of Zn is set to (50
4) It is difficult to terminate at the lower part of the active layer, the reproducibility is poor, and the Zn diffusion process is very time-consuming and not a highly productive method. It was Therefore, the present invention solves such a problem, and an object thereof is that the maximum light output is large because Eg in the window region is sufficiently larger than that in the light emitting region,
An object of the present invention is to provide a semiconductor laser which has a long life, high reliability, and can be easily manufactured with good reproducibility.

[Means for solving problems]

A method for manufacturing a semiconductor laser according to the present invention is at least the first method.
By the MOCVD method using the organometallic compound containing the group III element and the second organometallic compound containing the group III element as raw materials,
(A) a step of forming a first cladding layer above the single crystal semiconductor substrate, and (b) in a light absorption region of either the first or the second organometallic compound near the end face of the resonator. A step of forming an active layer on the first clad layer while irradiating ultraviolet light of a certain wavelength, and (c) a step of forming a second clad layer on the active layer. .

[Action]

According to the above configuration of the present invention, for example, the active layer is made of Al.
_{In the case of x} Ga _1-x As, the window region is Al _y Ga _1-y As (y> x)
Therefore, the difference in Eg is large enough that there is no carrier injection into the window region, and there is almost no optical absorption near the end face of the laser oscillation light, so there is no heat generation that occurs in the microcracks on the cleavage plane. The maximum optical output of the oscillated light is high, and the life during continuous oscillation can be dramatically extended. Further, since the light emitting region and the window region are formed at the same time, there is no laborious work such as the Zn diffusion process and the reproducibility is good.

〔Example〕

FIG. 1 is a main sectional view of a window type double hetero semiconductor laser according to an embodiment of the present invention. (102) n-type G
(103) n-type GaAs buffer layer, (104) n-type Al _0.4 Ga _0.6 As cladding layer, (109) Al _0.15 Ga _0.85 A on aAs substrate
s active layer, (105) P-type Al _0.4 Ga _0.6 As cladding layer, (10
The P-type GaAs cap layer of 6) and the n-type GaAs blocking layer of (107) are sequentially laminated by MOCVD. When the active layer is formed, the vicinity of the cleavage plane is irradiated with ultraviolet light, so that metalorganic raw materials such as trimethylgallium (hereinafter referred to as TMG) and trimethylaluminum (hereinafter referred to as TMA), which are group III raw materials of the MOCVD method, are formed. Since the decomposition efficiency of is different only in the light irradiation part, the aluminum content is high only near the cleavage plane.
An Al _0.2 Ga _0.8 As layer is formed on the (110) portion. After that, the blocking layer of (107) is etched in a stripe shape to form a P-type ohmic electrode of (108) and n of (101).
A type ohmic electrode is formed and cleaved in the vicinity of the light irradiation portion to form a resonator, so that a gain waveguide type semiconductor laser is obtained.

FIG. 2 shows the distribution of energy bands of the active layer in FIG. 1 in the direction of the optical resonator. Since the window region near the cleavage plane has a high aluminum content, the Eg of the light emitting region is sufficiently larger than the Eg of the window region. As a result, the laser light is hardly absorbed in the vicinity of the cleavage plane. Therefore, there is no concentration of optical power that causes destruction of the end face of the resonator, the maximum output of the semiconductor laser is large, and the life can be remarkably extended.

FIG. 3 shows a main configuration diagram of a window type double hetero semiconductor laser manufacturing apparatus. A raw material gas is introduced into the reaction tube of (310) from the raw material gas introduction system of (309), and is flown onto the heated substrate of (311) to grow a compound semiconductor thin film. To form the window region, the ultraviolet light from the (301) excimer laser is shaped by the (302) cylindrical lens and reflected by the (303) mirror during the growth of the active layer (30
4), (305) synthetic quartz lens to make a parallel beam.
The stripe pattern is focused on the substrate by the reduction lens of (307) through the mask on which the stripe pattern of (306) is formed.

As shown in FIG. 4, when the active layer is formed by the irradiation of (401) ultraviolet light, a window region having a large aluminum content of (403) is formed in a stripe shape. Cleavage (404) is performed so as to include the window region to form an optical resonator.

〔The invention's effect〕

As described above, according to the present invention, by forming the window region having a large energy gap, there is an effect that a semiconductor laser having a large maximum output and a long life can be obtained without deterioration of the cavity facet. Furthermore, since the window region can be formed at the same time when the active layer is formed, the steps such as thermal diffusion of Zn are completely unnecessary, and the production is significantly simplified. As a result, the yield of the high-power semiconductor laser is improved.

Furthermore, since there is a difference in refractive index between the light emitting region and the boundary of the window region in addition to the cleavage plane forming the optical resonator, there is an effect that the longitudinal mode is likely to be single.

[Brief description of drawings]

1 (a) to 1 (c) are main sectional views showing an embodiment of a window type double hetero semiconductor laser of the present invention. FIG. 2 is an energy band distribution diagram in the active layer cavity direction of the window type double hetero semiconductor laser of the present invention. FIG. 3 is a main block diagram of an apparatus for manufacturing a window type double hetero semiconductor laser of the present invention. 4 (a) and 4 (b) are views showing a part of the manufacturing process of the window type double hetero semiconductor of the present invention. FIG. 5 is a main sectional view of a conventional window type double hetero semiconductor laser. (101) ... n-type ohmic electrode (103) ... n-type GaAs buffer layer (106) ... P-type GaAs cap layer (107) ... n-type GaAs blocking layer (108) ... P-type ohmic electrode (302) ) …… Cylindrical lens (303) …… Dielectric multilayer film (304) …… Synthetic quartz concave lens (305) …… Synthetic quartz convex lens (308) …… High frequency oscillator (309) …… Gas supply system (310) …… Reaction Tube (312) …… Exhaust system (501) …… n-type ohmic electrode (502) …… n-type GaAs substrate

Claims (1)

[Claims] 1. A MOCVD method using, as a raw material, an organometallic compound containing at least a first group III element and a second organometallic compound containing a group III element. Forming a clad layer, and (b) irradiating the vicinity of the end face of the resonator with ultraviolet light having a wavelength in the light absorption region of either the first or second organometallic compound, 1. A method of manufacturing a semiconductor laser, comprising: a step of forming an active layer on the first clad layer; and (c) a step of forming a second clad layer on the active layer.