JPS6142987A - Manufacture of semiconductor laser - Google Patents

Abstract

PURPOSE:To obtain the title device excellent in electric properties and optical properties by a method wherein a stripe groove where the first upper clad layer is not exposed is formed by etching so as to suitably leave a light absorbtion layer after lamination of the first grown layer of an AlGaAs series semiconductor laser produced by an MBE device, and is then thermally cleaned. CONSTITUTION:After the lower clad layer 21, an active layer 22, the first upper clad layer 23, the light absorption layer 24 made of GaAs and an evaporation preventing layer 25 are successively laminated on the surface of a semiconductor substrate 10, the stripe groove 30 deep enough to leave the light absorption layer 24 and with a desired width is formed by photoetching. Next, the impurity deposited on the surface of the semiconductor substrate having the stripe groove 30 and said layer 24 which has been left are evaporated by thermal cleaning. Thereafter, the second upper clad layer 41 and a cap layer 42 are successively laminated on the surface of the substrate from which said impurity and the left layer 24 have been evaporated. Thereby, the laminated state of the second grown layer 40 can be improved regardless of the value of the Al composition of the first upper clad layer 23.

Description

Detailed Description of the Invention (a) Industrial Application Field The present invention relates to a method for manufacturing a semiconductor laser, and in particular, to a method for manufacturing a semiconductor laser.
The present invention relates to a method of manufacturing an AlGaAs semiconductor laser manufactured using a BE device.

(B) Prior art In recent years, a method of manufacturing a semiconductor laser using an MBE apparatus has been proposed.Here, we will briefly explain the case of manufacturing a semiconductor laser with a structure that requires two MBE growth steps, and , point out the problem.

First, after forming a first growth layer in the -th MBE growth step, the semiconductor substrate is taken out from the MBE apparatus, and a stripe of a predetermined width and a depth reaching the first upper cladding layer is formed in a photoetching step. Form a groove. As this photoetching step is performed, impurities such as oxides are directly attached to the etched portion (the surface of the first upper cladding layer), so these impurities are evaporated by a predetermined method. Thereafter, a second grown layer is laminated in a second MBE growth step.

Therefore, in the step of evaporating the impurities, if the A1 composition of the first upper cladding layer is 0.4 or more, the impurities such as the oxides are difficult to evaporate. Therefore, the stacked state of the second growth layer formed in the second growth step deteriorates, causing a problem that current no longer flows through this portion. On the other hand, the A1 composition of the first upper cladding layer is set to 0.
．． If it is less than 4, the state of the a-layer of the second grown layer is relatively good, but on the other hand, there arises a problem that the light confinement efficiency is reduced. Based on the above, it is difficult to manufacture semiconductor lasers with good electrical and optical properties using conventional methods.

(c) Purpose This invention provides a good lamination state of the second grown layer regardless of the value of the A1 composition of the first upper cladding layer, and facilitates the production of a semiconductor laser with good electrical and optical properties. The purpose of the present invention is to provide a method for molding a semiconductor laser that can be made easily.

(d) Structure The characteristic feature of the method for manufacturing the semiconductor laser according to the present invention is that the first growth layer is laminated in the first growth step, and then the light absorption layer is appropriately deposited in the photoetching step. The first upper cladding layer is etched to such a depth that the first upper cladding layer is not exposed, and the remaining light absorption layer and impurities attached to the surface of this light absorption layer are removed by a thermal cleaning process. The second growth layer was then removed in the second growth step.

(P) Embodiment FIG. 1 is an explanatory diagram showing an embodiment of the method for manufacturing a semiconductor laser according to the present 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 needle (not shown) and controlling the temperature and shutter of the evaporation source with a computer (not shown), N-type Al x
Lower cladding 1'U21 (A
1 composition X = 0.55) and the activity ff122 consisting of AI)
2), the first upper cladding layer 23 consisting of P-type AlXGa1~xAs (A1 group composition = 0.55), and N-type G
A light absorption layer 24 made of aAs and an N-type A 1 x Ga
Evaporation prevention Fi25 consisting of 1-xAs (A1 group composition
=0.35) is laminated on the semiconductor substrate 10 (first growth step).

(b) After the stacked semiconductor substrates 10 are taken out from the MBE apparatus, the back surface of the semiconductor substrates 10 is rough-finned. Next, the evaporation prevention layer 25 other than the portion where the stripe grooves are to be formed is covered with a photoresist 60. Using this photoresist 60 as a mask, the light absorption layer 24 is coated with the evaporation prevention layer 24 as appropriate (for example, about 1000 layers).
and the light absorption layer 24 are selectively etched to form stripe grooves 30 (photoetching step).

(C) The semiconductor laser 0 from which the photoresist 60 has been removed is organically cleaned. After that, the semiconductor substrate IO is again mounted in the MBE apparatus. Here, the semiconductor substrate 10 is heated at about 740° C. while being irradiated with an arsenic molecular beam. By continuing to do this for about 20 minutes, impurities such as oxides adhering to the surface of the semiconductor substrate 10 and the remaining light absorption layer 24 are evaporated (thermal cleaning step). However, since the optically absorbed N24 is also selectively evaporated, the surface of the first upper cladding layer 23 is exposed.

(d) In the state of step (C), the temperature of the semiconductor substrate 10 is set to about 6.degree.
1 (At composition Y=0.35) and a camp layer 42 made of P medium-sized GaAs is laminated (second growth step). Thereafter, a P-type electrode 50 and an N-type electrode 51 are formed in the same manner as in a normal semiconductor laser QgQ manufacturing method.

FIG. 2 shows the relationship between temperature and evaporation rate in the first upper cladding layer 23 and light absorption layer 24 described above. According to the figure, the first upper cladding layer 23
It can be seen that (AI x Ga1-xA5) hardly evaporates, but the evaporation rate of the light absorption layer 24 (GaAs) increases as the temperature increases.

In addition, in the above-mentioned embodiment, AI
Although the A1 composition of each layer consisting of s and A 1 y Ga 1-YAS is shown, it goes without saying that it can be changed as appropriate.

In addition, the lower cladding layer 21 and the first upper cladding layer 23
Since the A1 composition is set to 0.55, the light confinement effect between the lower cladding layer 21 and the first upper cladding layer 23 can be improved.

Furthermore, using this GaAs as passivation, AlxG
It goes without saying that the method of regrowing AI YGal-yAs on a1-)<As is not limited to semiconductor lasers and can be applied to other semiconductor devices.

(f) Effects In this invention, the first upper cladding layer has a passivation effect because the stripe grooves are formed in the photoetching process with a depth such that the light absorption layer remains appropriately. That is, impurities do not directly adhere to the first upper cladding layer during the photoetching process, and impurities and the remainder of the light absorption layer are evaporated during the thermal cleaning process, so that the surface of the first upper cladding layer is clean. be. As a result, the second grown layer has a laminated shape regardless of the value of the A1 composition of the first upper cladding layer! B can be improved.

Further, it has the remarkable effect that it does not require particularly high-precision technology and does not require an increase in the number of steps.

Based on the above, it becomes easy to manufacture semiconductor lasers with good electrical and optical properties.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an example of the method for manufacturing a semiconductor laser according to the present invention, and FIG. 2 is an explanatory diagram showing the relationship between the temperature and evaporation rate of the first upper cladding layer and the light absorption layer. . 10... Semiconductor substrate, 20... First growth layer, 21
...lower cladding layer, 22...active layer, 23...
First upper cladding layer, 24... Light absorption layer, 25...
- Evaporation prevention layer, 30... Stripe groove, 40... Second growth layer, 41... Second upper cladding layer, 42.
...Cap layer. Patent Applicant ROHM Co., Ltd. Agent Patent Attorney Takashi Ohnishi Figure 1

Claims (1)

[Claims] (1) In a method for manufacturing an AlGaAs semiconductor laser manufactured using an MBE apparatus, a lower cladding layer, an active layer, a first upper cladding layer, a light absorption layer made of GaAs, and an evaporation prevention layer are a first growth step of sequentially laminating layers on the surface of the substrate; a photoetching step of forming striped grooves with a desired width and a depth that leaves the light absorption layer; and a first growth step of forming layers on the surface of the semiconductor substrate on which the striped grooves are formed a thermal cleaning step of evaporating impurities attached to the semiconductor substrate and the remaining light absorption layer; and a second upper cladding layer on the surface of the semiconductor substrate from which the impurities and the remaining light absorption layer have been evaporated;
1. A method of manufacturing a semiconductor laser, comprising: a second growth step of sequentially laminating a cap layer.