JPH01293688A - Semiconductor laser - Google Patents

Abstract

PURPOSE:To prevent a defect of growth of a clad layer and to enhance an electrical characteristic by a method wherein a semiconductor layer where a diffraction grating is formed is to be of a multiple quantum well structure. CONSTITUTION:AlGaAs and GaAs are grown alternately on a substrate 1; a first clad layer 2a is formed; after that, a diffraction grating at a prescribed interval is produced in the layer 2. Then, a second clad layer 3 is crystal-grown on the produced diffraction grating; in addition, an active layer 4 and a third clad layer 5 are grown one after another. Then, electrodes 7, 8 are formed; an element is completed. The first clad layer 2a is not composed of only AlGaAs; GaAs which is hard to oxidize is laminated in every other layer; accordingly, the second clad layer 3 is grown normally at least on GaAs; a defect of growth is hard to cause; also the electrical conduction becomes good.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor laser equipped with a diffraction grating that reflects and diffracts a specific wavelength once.

[Conventional technology]

FIG. 2 is a sectional view showing an outline of the configuration of a conventional semiconductor laser equipped with a diffraction grating. In this figure, 1 is GaAs
2b is the first cladding layer made of Aj2GaAs, 3 is the second cladding layer made of AuGaAs, 4
is an active layer made of GaAs or Aj2GaAs, 5 is a third cladding layer made of AiLGaAs, 6 is a first electrode, and 7 is a second electrode.

Next, the manufacturing method will be explained.

First, a diffraction grating with a predetermined pitch is fabricated on the first cladding layer 2b crystal-grown on the substrate 1. Next, a second cladding layer 3.crystal is grown on the fabricated diffraction grating. Active layer 4. The third cladding layer 5 is sequentially formed. And finally, pole 6. Once the second electrode 7 is formed, the device is completed.

The basic operation of the semiconductor laser with this structure is the same as that of a normal one, and when a voltage is applied between the first electrode 6 and the second electrode 7 and a current is passed through the active layer 4, the inside of the active layer 4 is Although light emission and recombination occur, since a diffraction grating is provided on the first cladding layer 2b, it is possible to oscillate at a wavelength determined by the pitch of this diffraction grating.

[Problem to be solved by the invention]

A semiconductor laser equipped with a conventional diffraction grating as described above is
In order to obtain a desired refractive index, the first cladding layer 2b is made of AuG.
It is composed of aAs, and oxidation is inevitable when creating a diffraction grating. As a result, the second cladding layer 3 often suffers from poor growth, or even when it appears to have grown slightly, electrical continuity becomes defective.

This invention was made to solve these problems, and it provides a diffraction grating that is resistant to oxidation, does not cause growth defects in crystals grown on it, and does not impair electrical properties. The purpose of this invention is to obtain a semiconductor laser with the following characteristics.

[Means for Solving the Problems] In the semiconductor laser according to the present invention, the semiconductor layer on which the diffraction grating is fabricated has a multiple quantum well structure including a semiconductor layer that is difficult to oxidize.

[Effect]

In this invention, the entire surface of the diffraction grating is prevented from being oxidized, and the crystal grown on the diffraction grating is less likely to suffer from poor growth.

[Embodiment] FIG. 1 is a cross-sectional view showing a general configuration of an embodiment of a semiconductor laser of the present invention. In this figure, the same reference numerals as in FIG. 2 indicate the same things, and 2a is a first cladding layer as a semiconductor layer on which a diffraction grating is made, and is a multi-quantum layer made of thin films of AnGaAs and GaAs grown alternately. It has a well structure.

Next, the manufacturing method will be explained.

First, a first cladding layer 2a is formed by alternately growing AnGaAs and GaAs to a thickness of 100 Å or less on a substrate 1, and then a diffraction grating with a predetermined pitch is fabricated on the first cladding layer 2a. Next, the second cladding layer 3 is crystal-grown on the fabricated diffraction grating, but all of the first cladding layer 2a is not AJ:LGaAs, but GaAs, which is difficult to oxidize.
s are laminated layer by layer. Therefore, the second cladding layer 3 grows normally at least on GaAs, and growth defects are less likely to occur, and electrical conductivity is also improved. And after this, active layer 4. The third cladding layer 5 is sequentially grown, and the first electrode 6. Once the second electrode 7 is formed, the device is completed.

In this invention, the first cladding layer 2a is composed of GaAs and AJ2GaAs, but since these are laminated alternately so thinly as to cause a quantum effect, the band gap is equivalently wider than that of GaAs. Therefore, no loss occurs due to absorption of light by the active layer 4.

In addition, in the above embodiment, after the diffraction grating is manufactured, the active layer 4
Although the active layer 4 is grown as a crystal, a structure in which the active layer 4 is grown first and then the diffraction grating is fabricated can also produce the same effects as in the above embodiment.

〔Effect of the invention〕

As explained above, in this invention, the semiconductor layer on which the diffraction grating is fabricated has a multi-quantum well structure including a semiconductor layer that is difficult to oxidize. It has the advantage that it grows normally, is less likely to suffer from poor growth, and its electrical characteristics are not impaired.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the general structure of an embodiment of a semiconductor laser according to the present invention, and FIG. 2 is a cross-sectional view showing the general structure of a conventional semiconductor laser having a diffraction grating. In the figure, 1 is a substrate, 2a is a first cladding layer, 3 is a second cladding layer, 4 is an active layer, 5 is a third cladding layer, 6 is a first electrode, and 7 is a second electrode. Note that the same reference numerals in each figure indicate the same or corresponding parts. Agent: Masuo Oiwa (2 others) Figure 1, Figure 2, Figure 1, Indication of the case: Patent Application No. 128109-1988 2,
Title of the invention: Semiconductor laser 3, relationship to the amended case Patent applicant address: 2-2-3 Marunouchi, Chiyoda-ku, Tokyo. Name (601) Mitsubishi Electric Corporation Representative Moriya Shiki 4, Agent Address 2-2-3-5 Marunouchi, Chiyoda-ku, Tokyo
In Column 6 of the Brief Description of Drawings of the Specification Subject to Amendment, page 6, line 1 of the Specification of Contents of Amendment, r2a is amended to ``, and r2a, 2b are''. that's all

Claims (1)

[Claims] 1. A semiconductor laser equipped with a diffraction grating, characterized in that a semiconductor layer on which the diffraction grating is fabricated has a multiple quantum well structure including a semiconductor layer that is difficult to oxidize.