JPH01218085A - Semiconductor laser - Google Patents

Abstract

PURPOSE:To prevent occurrence of each unskillful p-n junction which is formed at a base of double channel parts and avoid leakage of an electric current, by making an n-type buffer layer grow thinly before forming a p-n-p current block layer in the process of a liquid phase epitaxy. CONSTITUTION:A multilayer structure consisting of an n-type buffer layer 2, an active layer 3, and a p-type clad layer 4 is formed by a liquid phase combined growth process on an n-type InP substrate 1. Then, two parallel grooves 5 (double channels) are formed in the multilayer by a photoresist process. After that, a p-n-p current block layer 6 as well as a cap layer 7 where the double channels are embedded grows by the second liquid phase epitaxy. In such a case, the current block layer 6 grows and its growth permits the n-type buffer layer 8 to grow thinly at the base of the double channels 5 before forming each p-n junction at the base of the channels 5. Thus, a semiconductor laser which is superior in characteristics is formed in such a way that no current leaks very much.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor laser used for optical fiber communications, and more particularly to a semiconductor laser having a structure including a buried layer with low leakage current.

[Conventional technology]

In conventional buried structure semiconductor lasers, a double channel is formed in a double heteroepitaxial layer that has a multilayer structure including a double heterojunction, and a p-n-p layer is directly formed in this part.
[Problem to be solved by the invention] The conventional buried structure semiconductor laser described above has a channel formed in a double heteroepitaxial layer. The p-n junction formed at the interface between the bottom of the substrate and the buried first Mi becomes poor due to thermal deterioration of the substrate surface during the thermal history process of the liquid phase growth process, which causes leakage current in the resulting semiconductor laser. There is a drawback that it is.

[Means to solve the problem]

The buried structure semiconductor laser of the present invention has a double channel in a multilayer structure having a double heterojunction, and has a structure in which this double channel is buried with a current blocking layer. 1
The structure is such that a buffer layer of the same conductivity type as the substrate is formed as the first layer of buried epitaxial growth at the interface between the layer and the bottom of the double channel.

In the present invention, instead of directly forming a current blocking layer at the bottom of the double channel, a buffer layer of the same conductivity type as the substrate is first formed, and then a current blocking layer with a p-n-p structure is formed. As a result, the first layer constituting the current blocking layer forms a p-n junction with the buffer layer rather than with the thermally degraded bottom of the double channel, so that the interface between the bottom of the double channel and the buried first layer of the current blocking layer The leakage current at the p-n junction can be reduced.

〔Example〕

Next, the present invention will be explained with reference to the drawings. Figure 0 is a longitudinal sectional view of one embodiment of the present invention.

An n-type buffer j [2, active layer 3,
A multi-N structure of p-type rad M4 is formed by liquid phase coupled growth.
R (double channel) 5 is formed in the multilayer structure. After this, the double channel 5 is formed by the second liquid phase growth.
p-n-p current blocking layer 6 and cap layer 7
grow. At this time, before growing the ρ-n-p current blocking layer 6 and forming a p-n junction at the bottom of the double channel 5, a thin n-type buffer layer 8 is grown on the bottom of the double channel 5, and then the p-n-type buffer layer 8 is grown thinly on the bottom of the double channel 5. n-p current blocking layer 6. The cap layer 7 is sequentially grown to form a semiconductor laser with good characteristics and low leakage current.

〔Effect of the invention〕

As explained above, in the present invention, even if the bottom of the double channel is thermally degraded by being exposed to high temperature before the growth starts in the liquid phase growth process, the process can be performed before forming the pn-p current blocking layer at the bottom of the double channel. Since the n-type buffer layer is grown thinly, generation of a poor p-n junction at the bottom of the double channel portion can be prevented, and a semiconductor laser with good characteristics without leakage current can be obtained.

[Brief explanation of the drawing]

The figure is a longitudinal sectional view of a semiconductor laser for explaining the present invention in detail. 1... InP substrate, 2... n-type buffer layer, 3...
... active layer, 4... p-type cladding layer, 5... double channel, 6... p-n-p current blocking layer, 7.
... Cap layer, 8... N-type buffer layer.

Claims (1)

[Claims] A multilayer structure in which a buffer layer, an active layer, and a cladding layer are sequentially laminated on a substrate is provided with two parallel grooves (double channel), and a p-n-p is further added to the multilayer structure having the grooves.
(or n-p-n) semiconductor laser comprising a current blocking layer and a cap layer, characterized in that a buffer layer having the same conductivity type as the substrate is provided below the lowest layer of the current blocking layer. semiconductor laser.