JP2550502B2 - Method for manufacturing single wavelength semiconductor laser - Google Patents

Description

The present invention relates to a semiconductor laser that oscillates at a single wavelength.

[Conventional technology]

FIG. 2 is, for example, Elect. Lett. 25 , 1989. pp. 220-221.
It is a cross-sectional side view which shows the structure of the conventional single wavelength semiconductor laser shown by page.

In the figure, (1) is a P-type InP substrate, (2) is an undoped InGaAsP active layer, (3) is an n-type InP cladding layer, and (4) is an island-shaped n-type with the periphery filled with InP. InGaA
It is an sP optical waveguide layer.

The conventional single wavelength semiconductor laser shown in FIG.
After sequentially forming an InGaAsP active layer (2), an n-type InP cladding layer (3), and an n-type InGaAsP optical waveguide layer (4) on an InP substrate (1), the InGaAsP optical waveguide layer (4) is formed at intervals of about 2000 Å. ) Are left as islands, the InGaAsP optical waveguide layer (4) is chemically etched to the n-type InP cladding layer (3), and then InGaAsP
It is manufactured by forming an n-type InP cladding layer (3) with P embedded therein.

 Next, the operation will be described.

When a voltage is applied to the upper and lower sides of this semiconductor element to inject electrons and holes into the active layer (2), radiative recombination occurs in the active layer (2) to emit light. This light is emitted near the active layer (2)
The island-shaped InGaAsP optical waveguide layer (4) embedded with P periodically presents feedback due to the periodic fluctuation of the equivalent refractive index due to the InGaAsP optical waveguide layer (4). This periodic variation of the equivalent refractive index has a function of increasing the amount of feedback of light of a specific wavelength and oscillating at a single wavelength, that is, wavelength selectivity. The intensity of this wavelength selectivity depends on the intensity of the periodic fluctuation of the refractive index, that is, the composition, thickness, and width of the periodically formed InGaAsP optical waveguide layer (4). In order to obtain an oscillating semiconductor laser device, it is necessary to control them.

In such a conventional semiconductor laser, chemical etching is used to periodically form the InGaAsP optical waveguide layer (4) in an island shape, so that the controllability of the shape of the InGaAsP optical waveguide layer (4) is poor and , InGaAsP optical waveguide layer (4) is made of a single composition of InGaAsP, and has a thickness of about 500Å and a width of about 1000Å
Therefore, it is not possible to adjust the shape of the optical waveguide layer by monitoring the shape of the optical waveguide layer after periodically forming the InGaAsP optical waveguide layer (4) by etching and adding etching according to the shape. It is difficult because the etching speed is too fast, and as a result, the intensity of periodic fluctuation of the refractive index, that is, the intensity of wavelength selectivity cannot be controlled, and a semiconductor laser that oscillates at a single wavelength cannot be obtained with high probability. There was a problem.

[Problems to be Solved by the Invention]

Since the conventional single-wavelength semiconductor laser device is configured as described above, the shape of the optical waveguide layer cannot be controlled, and therefore, there is a problem that a semiconductor element that oscillates at a single wavelength with high probability cannot be obtained. Atsuta

The present invention has been made to solve the above problems, and an object thereof is to obtain a semiconductor laser device that can control the shape of an optical waveguide layer and oscillates at a single wavelength with high probability.

[Means for solving the problem]

A method of manufacturing a single wavelength semiconductor laser according to the present invention,
A first step of forming an active layer on one main surface of a semiconductor substrate of the first conductivity type, a second step of forming a clad layer of the second conductivity type on the active layer, and a substantial step on the clad layer. A plurality of semiconductor layers each having an etching agent different in etching rate from each other in parallel alternately with one main surface of the semiconductor substrate to form a clutch layer to form an optical waveguide layer having a different refractive index, Using an etching agent corresponding to each semiconductor layer until the optical waveguide layer reaches a predetermined depth from the exposed surface toward the clad layer so that the optical waveguide layer periodically remains in the direction along the main surface of the semiconductor substrate. And a fourth step of etching each of the layers, and a fifth step of further laminating a clad layer and embedding the optical waveguide layer with the etched optical waveguide layer interposed therebetween.

[Operation] In the method for manufacturing a single-wavelength semiconductor laser according to the present invention, a plurality of semiconductor layers having etching agents having different etching rates are alternately laminated on a semiconductor substrate to form an optical waveguide layer. Each layer of the optical waveguide layer is formed by using an etching agent corresponding to each semiconductor layer until it reaches a predetermined depth from the exposed surface toward the cladding layer so that the optical waveguide layer is periodically left in the direction along one main surface of the semiconductor substrate. Since etching is performed, it is possible to control the distance between the optical waveguide layers that is periodically left during etching to be accurate.

〔Example〕

 An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional side view of a single wavelength semiconductor laser according to an embodiment of the present invention. In the figure, (1) is P-type In
P substrate, (2) InGaAsP active layer, (3) n-type InP cladding layer, (5) about 25Å n-type InGaAsP and about 25Å n-type I
It is an InGaAsP / InP optical waveguide layer with a thickness of about 500Å in which nPs are alternately formed.

InGaAsP and InP have different chemical properties, such as InGaAsP
Is etched by HNO ₃ but not by HCl, and InP is In
It has the opposite property of GaAsP. Therefore, as shown in this embodiment, an In layer in which about 25 Å InGaAsP and InP are alternately laminated is used.
By introducing the GaAsP / InP optical waveguide layer (5), the optical waveguide layer (5) is periodically formed, and then the shape is monitored.
The thickness of the optical waveguide layer (5) is set to 50 by selective etching so that the strength of the periodic fluctuation of the refractive index is appropriate according to the shape.
Å It can be adjusted in steps (10% of the whole), and as a result, it is possible to obtain a semiconductor element that oscillates at a single wavelength with high probability.

〔The invention's effect〕

As described above, according to the present invention, a plurality of semiconductor layers having etching agents having different etching rates from each other are alternately laminated on a semiconductor substrate to form an optical waveguide layer, and the optical waveguide layer is formed on one main surface of the semiconductor substrate. When etching the optical waveguide layer, each layer is etched with an etchant corresponding to each semiconductor layer until it reaches a predetermined depth from the exposed surface toward the clad layer so that it remains periodically along the direction. The distance between the optical waveguide layers left periodically can be controlled to be accurate, and a single-wavelength semiconductor laser with high wavelength selectivity can be formed.

[Brief description of drawings]

FIG. 1 is a sectional side view of a single wavelength semiconductor laser according to an embodiment of the present invention, and FIG. 2 is a sectional side view of a conventional single wavelength semiconductor laser. In the figure, (1) is a P-type InP substrate, (2) is an InGaAsP active layer, (3) is an n-type InP cladding layer, and (5) is an n-type IP layer.
This is an island-shaped n-type InGaAsP / InP optical waveguide layer in which nGaAsP and n-type InP are alternately formed in multiple layers. In the drawings, the same reference numerals indicate the same or corresponding parts.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Akira Takemoto 4-1-1 Mizuhara, Itami City, Hyogo Prefecture Mitsubishi Electric Corp. Optical / Microwave Device Research Center (72) Inventor Shoichi Kakimoto 4-chome Mizuhara, Itami City, Hyogo Prefecture No. 1 Mitsubishi Electric Corp. Optical / Microwave Device Research Center (56) References JP 63-263788 (JP, A) JP 63-136587 (JP, A)

Claims (1)

(57) [Claims] 1. A first step of forming an active layer on one main surface of a semiconductor substrate of a first conductivity type, a second step of forming a clad layer of a second conductivity type on the active layer, Third, a plurality of semiconductor layers each having an etching agent having a substantially different etching rate from each other are alternately laminated on the clad layer in parallel with the main surface to form an optical waveguide layer having a refractive index different from that of the clad layer. And the steps corresponding to each of the semiconductor layers until the optical waveguide layer has a predetermined depth from the exposed surface toward the cladding layer so that the optical waveguide layer periodically remains in the direction along the main surface. Fourth etching for each layer using the above etching agent
And a fifth step of further laminating the clad layer and burying the optical waveguide layer via the etched optical waveguide layer, the method of manufacturing a single wavelength semiconductor laser.