JPH0376289A - Manufacture of semiconductor laser - Google Patents

Abstract

PURPOSE:To make it unneeded to make an AlGaAs layer which serves as a guide layer small in the Al compositional ratio and to make oscillating laser rays shorter in wavelength by a method wherein a diffraction grating is formed on a wafer, and a second crystal growth is carried out in succession without exposing the wafer to atmosphere. CONSTITUTION:A wafer 100 where a double hetero-structure is formed is transferred into an etching chamber 30 kept in a high vacuum state and installed at a prescribed position. I2 gas is introduced into the chamber 30 by opening a gas leak valve 35 to set its inner pressure to 10mbr. Ar<+> ion laser rays are made to propagate through an optical fiber 31, the laser rays are split into two by a half mirror 32, the split laser rays are made to interfere with each other on the wafer 100, and the wafer 100 is exposed to the interfered laser rays for 30 seconds. As interfered light from two optical paths is periodically varies in intensity, an optically induced etching takes place periodically to form a diffraction grating 8 on a guide layer 6. In succession, the etching chamber 30 is made to return to be in a high vacuum state by a high vacuum pump 36, a gate valve 40 is opened, the wafer 100 is transferred into an MBE device 20 under high vacuum, and a second crystal growth is carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method of manufacturing a semiconductor laser incorporating a diffraction grating and having excellent single wavelength properties.

[Conventional technology]

As a semiconductor laser with a structure incorporating a diffraction grating,
DBR (distributed Bragg ref
(lector) laser, DFB (distributor) laser, DFB (distributor) laser,
ed feedback) lasers, etc. are well known, and these semiconductor lasers can improve single wavelength properties and are widely used for optical measurement, optical information processing, etc. In such a semiconductor laser, in order to exhibit the effect of providing a diffraction grating, the diffraction grating is placed near the active layer (approximately
3 μm or less. Therefore, as a crystal growth method during production, MOCVD (metalorganic chemical
cal vapor deposition: MBE (molecular bea
It is common to use a+epitaxy (molecular beam epitaxy) method. When manufacturing such a semiconductor laser, first, a double hetero layer including an active layer is crystal-grown on a substrate, then a diffraction grating is formed, and then a cladding layer and a cap layer are re-grown thereon.

However, when manufacturing an AlGaAs-based semiconductor laser, the AlGaAs layer is easily oxidized, so it is sometimes difficult to re-grow the ground layer and the cap layer. Therefore, in order to prevent oxidation, a GaAs layer or an AlvA layer, which is less susceptible to oxidation, is used as a surface layer during the first growth.
It is known that an AlGaAs layer with a small ratio is formed (Appl, Phys, Lett, 4B(1)
, 6 January 1986). In the manufacturing method disclosed in this document, the AI composition ratio is 0. An AlGaAs surface layer of 1 is formed as an oxidation prevention layer.

[Problem to be solved by the invention]

By the way, the wavelength of laser light commonly used in AlGaAs semiconductor lasers is 0.78 μm,
Since the active layer has an AI composition ratio of 0.15, the guide layer needs to have an AI composition ratio of 0.15 or more.

Since the AlGaAs layer is easily oxidized, the Al composition ratio of the AlGaAs layer that can be used as the guide layer must be kept low. Therefore, the conventional manufacturing method has a problem in that the wavelength of the laser light of the semiconductor laser that can be manufactured is limited.

The present invention has been made in view of the above circumstances, and a wafer on which a double hetero layer has been formed is subjected to photo-induced etching in an etching chamber with excellent airtightness to form a diffraction grating, and then the surface is exposed to air. Provided is a method for manufacturing a semiconductor laser, in which a diffraction grating can be formed and a ground layer and a cap layer can be formed by regrowth without limiting the wavelength of laser light by performing regrowth without exposure to The purpose is to

[Means to solve the problem]

A method for manufacturing a semiconductor laser according to the present invention is a method for manufacturing an AlGaAs semiconductor laser in which a double hetero layer two diffraction grating, a cladding layer, and a cap layer are formed in this order on a substrate. a step of growing and forming a double hetero layer, a step of subjecting the formed double hetero layer to photo-induced gas etching using an interference exposure light source to form the diffraction grating, and a step of forming the diffraction grating after the photo-induced gas etching without exposing it to the atmosphere. , a step of growing and forming the cladding layer and the cap layer.

[Effect]

In the method of manufacturing a semiconductor laser of the present invention, a double hetero layer including an active layer is first formed on a substrate, and then photo-induced gas etching is performed using an interference exposure light source to form a diffraction grating. Then, without exposing the surface to the atmosphere,
Re-grow the cladding and cap layers. Then, after the formation of the diffraction grating, the AlGaAs on the surface layer of the double hetero layer
This AlGa layer can be regrown without being oxidized.
There is no need to keep the Al composition ratio of the As layer low.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on drawings showing embodiments thereof.

FIG. 1 is a cross-sectional view showing the steps of the semiconductor laser manufacturing method according to the present invention, and FIG. 2 is a schematic diagram showing the configuration of an apparatus for carrying out the semiconductor laser manufacturing method of the present invention.

In Figure 2, 20 in the figure is MBB, which is the place of crystal growth.
The device 30 is a highly airtight etching chamber where a diffraction grating is formed, and the MBB device 20 and the etching chamber 30 are connected via a gate pulp 40.

An optical fiber 31 for propagating exposure light is inserted into the etching chamber 30, and a half mirror 32 is disposed near the end face of the optical fiber 31. In the optical path in two directions from the half mirror, ξ seats 33 and 34 are provided so that the reflected light from the mirrors 33 and 34 is irradiated onto the wafer 100 during the manufacturing process. Also, due to the action of the gas leak pulp 35 in the enching chamber 30, ■8
Gas is introduced, and the inside can be brought into a high vacuum state by the action of the vacuum pump 36.

First, in MBE chamber 2, the substrate temperature is set to 680° C. using the MBE method, and the following layers are successively grown on the n-GaAs substrate 1 to form a double heterostructure including an active layer. (Figure 1(a)).

2: n-GaAs buffer layer, thickness 1 μm IX-4
0"cs+-' (Si doped>3: n-A1.,
Gas, As cladding layer, film thickness 1μm5 XIO
"elm-" (Si doped) 4: undoped ^to,
lGas, lAs active layer.

Film thickness 0.1 μm 5: P-Al6.4 Gao, 6 As barrier layer,
Film thickness 0.02 μm5 XIO “am-” (Be doped) 6: p-/It0. zsGaa, t5As guide layer, film thickness 0.2 μm5 XIO"Ql-" (Be doped) 7: p-GaAs oxidation prevention layer, film thickness 0.05
μm5 Open the gas leak pulp 35 to introduce 2 gas into the room and reduce the internal pressure to 1.
Set to 0a+br (millibar). An Ar+ ion laser (λ-488 nm) is propagated through the optical fiber 31, the light is split by the half mirror 32, the laser light is caused to interfere with the surface of the wafer 100, and exposure is performed for 30 seconds. Then, since the interference light from the two optical paths forms periodic intensities on the wafer 100, photo-induced etching occurs periodically, and a diffraction grating 8 is formed on the guide layer 6 (FIG. 1(bl)).

Next, the inside of the etching chamber 30 is returned to a high vacuum state of IXl0-'mbr or higher again using the high vacuum pump 36, the gate valve 40 is opened, and the wafer 100 is transferred to the MB in the high vacuum.
Transfer to E device 20. Then, within the MBE device 20,
A second crystal growth (regrowth) is performed to form both of the layers described below. (Figure 1 (C)) 9: p-Al0.4 Ga, As kraft layer,
Film thickness 1μm5 Xl0I? cs+-' (Be doped)
10: p-GaAs cap layer, film thickness 1. crmI
XIO"cm-" (Be-doped) When performing the second crystal growth using an MOCVD device instead of an MBE device, after returning the inside of the etching chamber 30 to a high vacuum state, As is vapor-deposited on the surface of the wafer 100. Let me, MOCVD
The wafer 100 is transferred to the apparatus.

Then, the temperature of the substrate may be increased in the MOCVD apparatus to remove ^S from the surface, and then regrowth may be performed.

Next, by photo-etching, the craft layer 9 and the cap layer 10 in the center are formed into a mesa structure with a width of 4 μm. The etching conditions at this time are the etching solution 4HsPO**
HzO□+cnsou was used for 40 seconds at room temperature.

Next, the substrate temperature was set to 400°C, and 5iHe (11/ll
l1n,)+0g (0.4Il/sin,) for about 3 minutes to form a 5i film with a film thickness of 5000 on the diffraction grating 8 (guide layer 6) exposed by etching.
An Oz thermal CVD film 11 is formed. After making a window with a diameter of 3 μm on the top of the mesa by photoetching, Au/C
A p-side electrode 12 made of r is formed. Finally, after removing the substrate 1 by lapping to about 100 μm, the AuGe/Ni
An n-side electrode 13 made of /Au is formed to produce a laser element (FIG. 1(d)).

I- of the semiconductor laser manufactured using the manufacturing method of the present invention
The L (current-light output) characteristic is shown in FIG.

The oscillation threshold current I was 45 mA. Further, FIG. 4 shows the temperature dependence of the oscillation wavelength in a semiconductor laser manufactured using the manufacturing method of the present invention. As can be seen from FIG. 4, the oscillation spectrum was a single wavelength, and the rate of change of the oscillation wavelength with respect to temperature change was 0.85 A/°C.

As described above, the semiconductor laser manufactured according to the present invention has good characteristics.

〔Effect of the invention〕

As detailed above, in the semiconductor laser manufacturing method of the present invention, after forming the diffraction grating, the second crystal growth is performed continuously without exposing it to the atmosphere. It is no longer necessary to reduce the AI composition ratio of the AlGaAs layer, the oscillation wavelength can be shortened, the resist coating and removal steps can be omitted, and the active layer can be formed using the MBE method or MOCVD method. Diffraction gratings can also be formed in the lower layer, etc.
The present invention has excellent effects.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing the steps of the method for manufacturing a semiconductor laser according to the present invention, FIG. 2 is a schematic diagram showing an apparatus for carrying out the method for manufacturing a semiconductor laser according to the present invention, and FIG. A graph showing the IL characteristics of a semiconductor laser manufactured using the
FIG. 4 is a graph showing the temperature dependence of the oscillation wavelength in a semiconductor laser manufactured using the manufacturing method of the present invention. 1...Substrate 4...Active layer anti-oxidation layer...Cap layer 2...Buffer N 3...Clad layer 5...Barrier layer 6...Guide layer 7...8... ·Diffraction grating
9...Clad N1020...? lBB device 30
・・・Etching home ownership permit applicant

Claims (1)

[Claims] 1. A method for manufacturing an AlGaAs semiconductor laser in which a double hetero layer, a diffraction grating, a cladding layer, and a cap layer are formed in this order on a substrate, comprising: the double hetero layer on the substrate; forming the diffraction grating by subjecting the formed double hetero layer to photo-induced gas etching using an interference exposure light source; and after the photo-induced gas etching, removing the cladding from the cladding without exposing it to the atmosphere. 1. A method for manufacturing a semiconductor laser, comprising the step of growing a layer and a cap layer.