JPH01109778A - Formation of low reflectivity edge face of optical element - Google Patents

Abstract

PURPOSE:To improve reliability, by epitaxially growing a lower clad layer, an active layer and an upper clad layer on a substrate, in which a deep groove is formed by etching, cleaving the device at the center of the groove in parallel with the groove, and isolating elements. CONSTITUTION:A groove 5 is formed in a semiconductor substrate 1 by etching. Thereafter, at least a lower clad layer 2, an active layer 3 and an upper clad layer 4 are epitaxially grown sequentially on the semiconductor substrate 1. The device is cleaved at the center of the groove 5 in parallel with the groove, and elements are isolated. Therefore the surface of an epitaxial layer 6 is inclined at the end surface of the extended flat part of the active layer 3. Thus a very low reflectivity is obtained. Since the vicinity of the edge face becomes a window structure, deterioration of the edge face due to the absorption of light is hard to occur. In this way, a highly reliable optical element can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Applications] The present invention relates to a method for forming low reflectance end faces of optical elements such as edge-emitting LEDs and LDs.

[Conventional technology]

In an edge-emitting optical element, a conventional method for forming an end face with a low reflectance is to apply a non-reflective coating to the end face.

FIG. 2 is a cross-sectional view of an edge-emitting type optical device in which a non-reflection coating film is formed on the edge surface.

In this figure, 1 is an n-InP substrate, 2 is an n--1n
The P lower quail cladding 3 is an InGaA sP active layer (hereinafter simply referred to as an active layer. The same names apply to other symbols), 4 is a p-InP upper cladding layer, and 7 is a non-reflection coating film.

Anti-reflection coating film 7 let S i O,,S
iN,.

2.0. The active layer 3 is formed with a thickness of λ/4 relative to the wavelength λ of the light generated in the active layer 3 by electron beam evaporation or sputtering. Such an anti-reflection coating film 7 is applied to the open end surface.
By forming this, it is possible to obtain an end face with a low reflectance of about lo-3.

Another method for forming end faces with low reflectivity is to form the end faces obliquely by etching as shown in FIG. That is, in FIG. 3, 8 is an etched end face, and the other parts are the same as in FIG. 2. The end surface of the active layer 3 on the etched side is oblique,
Furthermore, since the active J83 is not a mirror surface, the light propagating through the active J83 is diffusely reflected at the end face. Therefore, a low reflectance of about 10@-4 can be obtained at the etched end face.

[Problem that the invention seeks to solve]

The edge-emitting optical element configured as described above, such as an edge-emitting LED, must not emit laser even at a low temperature of -40°C. In order to suppress laser oscillation at −40° C., it is necessary to reduce the reflectance of one end face to about 10 −4 or less. However, as shown in Figure 2,
In the method of forming the non-reflection coating film 7 on the cleaved end face, the reflectance (L) is 0-31\i degrees, and it is difficult to realize a low reflectance of 101 or less.

On the other hand, as shown in Fig. 3, the method of etching the end face to reduce the reflectance has the problem that the etched end face has more non-radiative recombination centers than the straight seven-opening end face, so it is more likely to cause the straight edge to become S. was there.

This invention was made in order to solve the above-mentioned problem, and it is possible to realize an extremely low reflectance of about 10-' or less, and also to create a highly reliable optical element that does not cause end face deterioration. 1. [Means for solving the problem] A method for forming a low reflectance end face of an optical element according to the present invention is to provide a method for forming a reflectance end face by etching a semiconductor substrate, and then forming a groove. , a layer including at least a lower cladding layer, an active layer, and an upper cladding layer is epitaxially lengthened on the semiconductor substrate, and then the center of the groove is formed so that the end face on the extension of the flat part of the active layer becomes an inclined surface of the growth layer. The device is then cleaved parallel to this groove to perform element isolation.

[Effect]

In this invention, a lower cladding layer, an active layer, and an upper cladding layer are epitaxially grown on a substrate in which a deep groove is formed by etching, and the active layer is separated by cleavage parallel to the groove at the center of the groove. The end face on the extension of the flat part becomes the inclined surface of the epitaxial layer, making it difficult for end face deterioration to occur.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1(a) to 1(C).

FIGS. 1A to 1C are cross-sectional views illustrating a method for forming a low reflectance end face of an optical element according to the present invention. In this figure, the same reference numerals as in FIG. 2 indicate the same parts.

First, as shown in FIG.
A groove 5 having a width of approximately 40 μm is formed by etching. Next, as shown in FIG. 1(b), the lower cladding layer 2. Active layer 3. The upper cladding layer 4 is grown sequentially.

At this time, in the groove 5 part, the cladding layers 4 and 7 are 3 degrees above the active layer.
45 is curved as shown, the groove 5 is not completely filled, and the surface becomes an inclined surface. First, as shown in FIG. 1(C), an edge-emitting optical device manufactured by a manufacturing method in which the groove 5 is cleaved parallel to the groove 5 to separate the elements by an angle of 3° or more is used. (, t1 The active layer 3 is curved at the cleaved groove part, and the end face on the extension of the flat part of the active layer 3 faces the inclined epitaxial layer 6. Therefore, the inside of the active layer 3 is curved. For the guided light, the structure is such that the optical waveguide mechanism disappears before the end face on the ζ and t1 groove side, and
Since the end face is inclined and light is diffusely reflected, the reflectance at the end face on the groove side is extremely low (and a reflectance of about 10 −4 can be easily obtained).

Furthermore, since the end face is the surface of the epitaxial layer 6, there are fewer non-radiative recombination centers on the end face formed by etching. Moreover, since the light guided through the active layer 3 travels to the upper cladding layer 4, which has a larger band gap than the active layer 3, near the end face, no light absorption occurs. Therefore, near the end face, end face deterioration due to light absorption is likely to occur (
, a highly reliable optical device can be obtained.

〔Effect of the invention〕

As explained above, in the present invention, after forming a groove in a semiconductor substrate by etching, epitaxial layer lengths (lower cladding layer, active layer, and upper cladding layer) are sequentially formed on the semiconductor substrate to form a groove in the center of the groove. Since the device is separated by cleavage parallel to this groove, the end face on the extension of the flat part of the active layer becomes an inclined epitaxial 1d surface, which makes it possible to achieve extremely low reflectance. Since it has a window structure, end face deterioration due to excessive absorption occurs (<, which has the effect of obtaining a highly reliable optical element.

[Brief explanation of the drawing]

1(a) to (C) are process cross-sectional views showing a method for forming a low reflectance end face of an optical device according to an embodiment of the present invention, and FIG. FIG. 3 is a sectional view illustrating a method of forming a reflectance end face. FIG. 3 is a sectional view illustrating a method of forming a low reflectance of an optical element by conventional end face etching. In the figure, 1 is an n-1nP substrate, 2 +, in -I
nP lower Cla-Sodo layer, 3 is InGaA sP active layer,
4 is a groove on the p-InP cladding layer, and 6 is an evixial layer. The same reference numerals in each figure indicate the same or corresponding parts. Agent Masu Oiwa (2 others) Figure 1 Figure 2

Claims (1)

[Claims] A step of forming a groove in a semiconductor substrate by etching, a step of epitaxially growing a layer including at least a lower cladding layer, an active layer, and an upper cladding layer on the semiconductor substrate, and a step of growing an end face on an extension of a flat portion of the active layer with a slope. A method for forming a low reflectance end face of an optical element, the method comprising the step of separating the elements by cleaving at the center of the groove and parallel to the groove so as to form a layer surface.