JPS6142985A - Semiconductor laser and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain the title device of good controllability in lateral mode and vertical mode by a method wherein an evaporation preventing layer made of AlGaAs with a specified Al composition is formed on the surface of a light absorption layer in an AlGaAs series semiconductor layer produced by an MBE device. CONSTITUTION:A semidonductor substrate 10 made of N type GaAs is provided with the lower clad layer 20 made of N type Al1xGa1-x1As, an active layer 21 made of Alx2Ga1-x2As, the first upper clad layer 22 made of P type Alx3Ga-x31As, and the light absorption layer 23 made of N type GaAs; then, the evapoation preventing layer 24 made of Alx4Ga1-x4As with an Al composition set at X4>0.1. The second upper clad layer 25 made of P type AlyGa1-yAs is increased to a film thickness almost the same as that of the lamination of the fist upper clad layer 22, light absorption layer 23, and evaporation preventing layer 24; further, the light absorption layer 23 and the evaporation preventing layer 24 form a stripe groove 30 by being selectively etched. This manner can yield the semiconductor laser of good controllability in lateral mode and vertical mode by making effective the light absorbing effect of the light absorption layer.

Description

Detailed Description of the Invention (a) Industrial Application Field The present invention relates to a method for dipping a semiconductor laser in W, and in particular, to a method for dipping a semiconductor laser in W.
A1. manufactured by BE equipment. The present invention relates to a method of manufacturing a GaAs semiconductor laser.

(B) Prior Art In recent years, methods have been proposed for manufacturing semiconductor lasers with a structure that takes into consideration controllability of transverse and longitudinal modes and mass production using an MBE apparatus.

Normally, to manufacture a semiconductor laser using an MBE apparatus, a -th MBE growth step, a photoetching step for forming striped grooves, and a second MBE growth step are performed.

For example, in the photo-etching process, a problem arises in that impurities such as oxides adhere to the surface of the semiconductor substrate. Therefore, it was necessary to remove the impurities before the second MBEIIj, long process. However, in the conventional impurity removal method, the stacked state of the grown layers becomes very poor in the second MBE growth step.

Therefore, a so-called thermal cleaning process (heating the semiconductor substrate to a high temperature while exposing it to an arsenic molecular beam) was devised.

When this thermal cleaning process is performed, the second MB
The stacked state of the layers grown by the E growth process can be improved. Therefore, it is very important to perform this thermal cleaning process.

In this type of semiconductor laser, a light absorption layer made of GaAs is usually grown last in the -th MBE growth step. However, since the light absorption layer has a characteristic that its evaporation rate increases as the temperature rises (see FIG. 3), the light absorption layer is evaporated during the thermal cleaning process performed at high temperature. However, it is virtually impossible to perform a thermal cleaning process, and it has been difficult to manufacture a semiconductor laser with good controllability in transverse mode and longitudinal mode.

(C) Objective The first object of the invention is to provide a semiconductor laser that has good controllability in transverse mode and longitudinal mode.

The second invention aims to provide a method for manufacturing a semiconductor laser that prevents evaporation of the light absorption layer during the thermal cleaning process and improves the lamination state of the grown layers in the second MBE growth process. .

(D) Structure The semiconductor laser according to the first invention has an A1 composition of 1>, 1
It is characterized in that an evaporation prevention layer made of 81 x 4 Ga1-y4 8S with a concentration of >0.1 is formed on the surface of the light absorption layer.

A method for manufacturing a semiconductor laser according to a second aspect of the invention includes: a first growth step of continuously laminating layers up to the evaporation prevention layer on the surface of a semiconductor substrate; a photoetching step of forming stripe grooves on the layered semiconductor substrate; a thermal cleaning step of evaporating impurities attached to the surface of the semiconductor substrate on which the stripe L+5 has been formed; and a second growth step of laminating a second upper cladding layer and a cap layer on the semiconductor substrate from which the impurities have been evaporated. It is characterized by having the following.

(e) Example Plate Rich Blood Plate FIG. 1 is a sectional view showing an embodiment of a semiconductor laser according to the first invention.

In the figure, 1 is a semiconductor laser, 10 is an N-type GaAs
20 is an N-type semiconductor substrate consisting of lX+Ga1
Lower cladding layer consisting of −X+8, 21 is 81X
2 Active layer made of Ga1-x2As, 22 is P-type AI
A first upper cladding layer made of X 3 cal-X3^S, 23 a light absorption layer made of N-type GaAs, and 24 a N
This is an evaporation prevention layer made of type Al x a cal-X4 As. Reference numeral 25 denotes a second upper cladding layer made of P-type AlYGa1 and As, which is similar to the first upper cladding layer 2.
2. The film thickness is approximately the same as that of the laminated film of light absorption N23 and evaporation prevention Fi24. The light absorption layer 23 and the evaporation prevention layer 24 are selectively etched to form striped grooves 30. 26 is a cap layer made of P-type GaAs. 40 is a P-type electrode made of Ti and ΔU, and 41 is an N-type electrode made of AuGe.

FIG. 2 is an explanatory diagram showing an example of the manufacturing method according to the second invention.

(a) N-type G installed in the MBE device (not shown)
A semiconductor substrate 10 made of aAs is heated by a predetermined method.

The raw materials and impurities put into the evaporation source are evaporated in the form of molecular beams. By monitoring this raw material with a mass spectrometer (not shown) and controlling the temperature and shutter of the evaporation source with a computer (not shown), N-type ^lx + Ga
A lower cladding layer 20 made of 1-X+ As and an AI
An active layer 21 made of X 2 Ga1-)l As and P
A first upper craft layer 22 made of type AI X 3 Ga1-x3 As and a light absorption layer 2 made of N type GaAs.
3 and N type A1. An evaporation prevention layer 24 made of X4Gal-X4As is laminated on the semiconductor substrate 10 (first growth step). In this case, the A1 composition of each layer is, for example, X is 0.50, ×2 is 0.12, ×3 and ×
4 is set to 0.35.

(b) After the stacked semiconductor substrates 10 are taken out from the MBE apparatus, the back surface of the semiconductor substrate Fi 10 is lapped. Next, the surface of the evaporation prevention layer 24 other than the portion where the stripe grooves are to be formed is covered with a photoresist 50. Using this resist 50 as a mask, the evaporation prevention layer 24 and the light absorption layer 23 are selectively etched until the first upper cladding layer 22 is reached, thereby forming striped grooves 30.

(C1 Semiconductor substrate 1 from which the photoresist 1-50 has been removed)
0 is organically washed. After that, the semiconductor substrate 10 is again
Install it inside the BE device. Here, the semiconductor substrate 10 is heated at about 740° C. while being exposed to an arsenic molecular beam.

By continuing to do this for about 15 minutes, impurities such as oxides adhering to the surface of the semiconductor substrate 10 are evaporated (thermal cleaning step). Although the first upper cladding layer rrJ22 is exposed in the stripe groove 30 portion, the evaporation rate of the first upper cladding layer 22 is very slow and hardly evaporates. On the other hand, since the light absorption layer 23 has an evaporation prevention layer 24 deposited on its surface, evaporation is prevented.

(d) In the state of step (C), the temperature of the semiconductor substrate IO is set to about 600°C, and the P-type Δ1yG
A second upper cladding layer 25 made of al-YAs and P
A cap layer 26 made of 10-type GaAs is laminated on the surface of the evaporation prevention layer 24 in which the stripe grooves 30 are formed (second growth step). In addition, even if the composition is 0.
I set it to 35. Thereafter, electrodes 40 and 41 are formed in the same manner as in a normal semiconductor laser manufacturing method.

Therefore, the light absorption layer 23 and the evaporation prevention layer 24 (A
Figure 3 shows the relationship between temperature and evaporation rate when the composition is 0.1 or higher. As shown in the figure, it can be seen that the evaporation prevention layer 24 hardly evaporates. It can be seen that the evaporation rate of the light-absorbing JW23 (GaAs) increases as the temperature increases.

In addition, in the embodiments of the first and second inventions described above,
The width of the stripe groove 30 and the thickness of the first upper cladding layer 22 control the transverse mode and longitudinal mode of the semiconductor laser.

(to) Effect The first invention has an A1 composition of X on the surface of the light absorption layer.

Since the evaporation prevention layer made of 8lX4Ga1-X4ΔS with 4>0.1 was formed, the light absorption effect of the light absorption layer can be made effective. Therefore, it is possible to provide a semiconductor laser with good controllability in transverse mode and longitudinal mode.

According to the second invention, the evaporation prevention layer can substantially prevent the light absorption layer from evaporating during the thermal cleaning process. Therefore, based on the fact that the thermal cleaning process can be performed well, it is possible to improve the lamination state of each layer in the second MBE growth process. the result,
A semiconductor laser as described above can be easily manufactured.

Furthermore, since the evaporation prevention layer is made of AlGaAs, it can be grown continuously with other layers using an MBE apparatus. Therefore, there is an effect that no special manufacturing method is required, and there is no need to increase the number of manufacturing steps.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an embodiment of the semiconductor laser according to the first invention, FIG. 2 is an explanatory diagram showing an embodiment of the manufacturing method according to the second invention, and FIG. 3 is a diagram showing the temperature of the semiconductor substrate. FIG. 3 is a characteristic diagram showing the relationship between H and total speed. ■...Semiconductor laser, 10...Semiconductor substrate, 20
... lower cladding layer, 21 ... active layer, 22 ...
First upper crat lfj, 23... light absorption layer, 21
1... Evaporation prevention layer, 25... Second upper crat I
"17.26...Cap 屓. Patent applicant: ROHM Co., Ltd. Agent, Patent attorney: Takaharu Ohnishi Figure 1: 21'4 Figure 3: Hanchimura Nyo; 1 ('C)

Claims (2)

[Claims] (1) In an AlGaAs semiconductor laser manufactured using an MBE apparatus, a lower cladding layer made of Al_X_1Ga_1_-X_1As, an active layer made of Al_X_2Ga_1_-_X_2As, and an Al_X_3Ga_1_-_X_3As
a first upper cladding layer made of GaAs, a light absorption layer made of GaAs, and Al_X_ with a composition ratio of _X_4>0.1.
A first growth layer formed by sequentially stacking an evaporation prevention layer made of 4Ga_1__X_4As on the surface of a semiconductor substrate, and a first growth layer formed by photo-etching to a depth reaching the first upper cladding layer and a desired width. stripe grooves, and A on the surface of the first growth layer in which the stripe grooves are formed.
A semiconductor laser comprising a second growth layer formed by sequentially stacking a second upper cladding layer made of l_YGa_1_-_YAs and a cap layer made of GaAs with a high impurity concentration. (2) In a method for manufacturing an AlGaAs semiconductor laser manufactured using an MBE apparatus, a lower cladding layer made of Al_X_1Ga_1_-_X_1As, an active layer made of Al_X_2Ga_1_-_X_2As, and an Al_X_3Ga_1_-_X_3A
A first upper cladding layer made of S, a light absorption layer made of GaAs, and Al_X with a composition ratio of _X_4>0.1.
A first growth step of laminating an evaporation prevention layer made of _4Ga_1_-_X_4As on the surface of the semiconductor substrate; a photo-etching process to form striped grooves of a certain width; a thermal cleaning process to evaporate impurities attached to the surface of the semiconductor substrate on which the striped grooves have been formed;
A method for manufacturing a semiconductor laser, comprising: a second growth step of laminating a second upper cladding layer made of YAs and a cap layer made of GaAs with a high impurity concentration.