JPH06326409A - Surface emission element - Google Patents

Abstract

PURPOSE:To obtain a surface emission element in which the direction of polarization is prescribed in one direction. CONSTITUTION:After an n-type GaAs/AlAs multilayer reflection film 20, an n-type GaAs layer 11, an In0.2Ga0.8AS active layer 12, a P-type GaAs clad layer 13, and a P-type GaAs/AlAs multilayer reflection film 21 have grown successively on an n-type GaAs substrate 10, an etching treatment is conducted in such a manner that a square is formed when a part of the P-type GaAs/AlAs multi- layer film 21, the P-type GaAs clad layer 13, the In0.2Ga0.8 active layer 12, the n-type GaAs layer 11 and the n-type GaAs/AlAs multilayer reflection film 20 are viewed from above the element. After an insulating film 22 has been selectively formed, a gold film 23, as a film having the thermal expansion coefficient different from a semiconductor layer is selectively formed on the upper part of the element. An anode electrode 31 is formed covering the P-type GaAs clad layer 12 and the P-type GaAs/AlAs multilayer reflection film, and also a cathode electrode 30 is formed on the n-type GaAs/AlAs multilayer reflection film 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface emitting device for optical transmission and optical information processing.

[0002]

2. Description of the Related Art Research on a semiconductor laser, which is a light source for optical transmission and optical information processing, is under way. Among them, the surface-type semiconductor laser (1) is capable of forming a monolithic resonator,
(2) Wafer-by-wafer inspection before element separation is possible, (3)
It features dynamic single-wavelength operation, (4) large emission area, narrow emission circular beam, (5) high-density two-dimensional laser array, and (6) integration of three-dimensional array device by stacking. A pioneering research was conducted by Iga et al. On the surface-type semiconductor laser, and the results of their series of research are 1988.
Published by Iga et al., Journal of Quantum Electronics (Journal of Quantum)
(Electronics) Vol. 24, page 1845, including historical background.

Further, the surface-type optical functional element is an element for performing optical information processing by making use of the advantages of the surface-type semiconductor laser described above.
It is expected to enable two-dimensional parallel optical information processing aiming at large-capacity information processing. As one of such surface-type optical functional elements, there is a vertical resonator type surface-input / output optoelectronic device, which is referred to by Numai et al., Applied Physics Letters (Applied Phy).
Sics Letters) Volume 58, page 1250 can be cited.

[0004]

However, the conventional surface emitting device has the following problems. In conventional surface-emitting devices, the optical waveguide is not formed along the traveling direction of the light, so the polarization direction of the emitted laser light is different due to slight asymmetry of the device structure. The polarization direction was different for each element.
On the other hand, when the emitted light is coupled with another optical circuit element, it is necessary to define the polarization direction of the emitted light in a specific direction in order to improve the coupling efficiency.

Therefore, an object of the present invention is to realize a surface emitting device in which the polarization direction is defined in one direction.

[0006]

The surface emitting device of the present invention comprises:
A layer having a thermal expansion coefficient different from that of the active layer or a layer having a lattice constant different from that of the active layer is selectively or asymmetrically formed above the active layer.

[0007]

Consider a case where a layer having a coefficient of thermal expansion different from that of the active layer, for example, a dielectric or a metal film is selectively formed above the active layer. 200 ℃ when forming dielectric film or metal film
Although the temperature becomes high as described above, when the element temperature is lowered to room temperature after forming the film, distortion occurs due to the difference in expansion coefficient. Moreover, since the film is selectively formed, the strain applied to the crystal becomes asymmetric. As a result, the bandgap is deformed according to the orbit-distortion operator, and the polarization is directionally dependent on the optical transition.

Even when a layer having a lattice constant different from that of the active layer is selectively formed, the strain applied to the crystal is asymmetrical as in the above description, so that the polarization is controlled.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS This embodiment will be described in detail with reference to the drawings. FIG. 1 is a diagram showing a structure of a surface emitting device according to a first embodiment of the present invention.

The structure of this embodiment will be described below in accordance with the manufacturing procedure. First, the structure of the first embodiment will be described with reference to FIG. 1A is a top view and FIG. 1B is a cross-sectional view. An n-type GaAs / AlAs multilayer reflection film 20 and an n-type GaAs layer 1 are formed on an n-type GaAs substrate 10 by molecular beam epitaxy (hereinafter abbreviated as MBE).
_{1, In 0. 2 Ga 0} . 8 As active layer 12, p-type GaA
The s clad layer 13 and the p-type GaAs / AlAs multilayer reflective film 21 are sequentially grown. After that, p-type GaAs / AlAs
Multilayer film 21, p-type GaAs cladding layer 13, In _{0. 2}
Ga _0.8 As active layer (thickness 80 Å) 1
2. Part of the n-type GaAs layer 11 and the n-type GaAs / AlAs multilayer reflection film 20 is etched so as to have a square shape when viewed from above the element. After a silicon nitride film is selectively formed on the side wall as the insulator 22, gold and Au 23 are selectively vapor-deposited at a high temperature on the upper part of the device. After vapor deposition, after cooling to room temperature, the p-type GaAs cladding layer 12 and p-type GaA
An anode electrode 31 is formed so as to cover the s / AlAs multilayer reflective film 21. The anode electrode 31 on the p-type GaAs / AlAs multilayer reflective film 21 functions as a metal reflective film. Further, the cathode electrode 30 is formed on the n-type GaAs / AlAs multilayer reflective film 20.

FIG. 2 is a diagram showing the measurement results of the first embodiment. The oscillation threshold current is 1 mA or less. The polarization of the emitted light is parallel to the short side of the selectively formed gold 23, and the ratio of the light intensity with the polarization orthogonal to this (P (parallel) / P (orthogonal)) is 1: 100. And it is a good linear polarization.

FIG. 3 is a diagram showing the structure of a surface emitting element according to the second embodiment of the present invention. The difference from the first embodiment is that the strained semiconductor layer 24 is deposited on the upper part of the device instead of depositing the whole 23 at a high temperature.
As an In _{0. 2} Ga _0. Is to the ₈ AS100 Angstroms are selectively formed. Even in this case, the same effect as the first embodiment is obtained.

Although gold is used as the layer having a different expansion coefficient from that of the semiconductor layer in the first embodiment, any layer having a different expansion coefficient from that of the semiconductor may be used. It is not necessary to limit the semiconductor material to the above-mentioned GaAs system, either.
It may be an nP-based material. Further, the multilayer reflective film is not limited to a semiconductor and may be a dielectric or the like as long as the material can even increase the reflectance.

Further, in this embodiment, gold 2 is formed on the upper part of the element.
3 and the strained semiconductor layer 24 are partially formed to create asymmetry, but a plurality of layers or strained semiconductor layers having different thermal expansion coefficients may be formed on the upper part of the element to generate asymmetry. For example, gold 23 may be formed in the upper half of the element and the strained semiconductor layer 24 may be formed in the other half.

[0015]

As the surface emitting element, it is possible to realize an element in which the polarization direction is defined in one direction. This can improve the coupling efficiency with other optical circuit elements. Further, it is effective for application to an optical integrated device and an optical logic device.

[Brief description of drawings]

FIG. 1 is a diagram showing a structure of a surface emitting element according to a first embodiment of the present invention.

FIG. 2 is a diagram showing measurement results of the first example of the present invention.

FIG. 3 is a diagram showing a structure of a surface emitting element according to a second embodiment of the present invention.

[Explanation of symbols]

 10 semiconductor substrate 11 n semiconductor layer 12 strained quantum well active layer 13 p semiconductor layer 20 n semiconductor multilayer film 21 p semiconductor multilayer film 22 insulator film 23 gold 24 strained semiconductor layer 30 electrode 31 electrode

Claims (2)

[Claims] 1. A surface emitting semiconductor device, wherein a layer having a thermal expansion coefficient different from that of the active layer or a semiconductor layer having a lattice constant different from that of the active layer is selectively formed above the active layer. Surface emitting element. 2. In a surface emitting semiconductor device having a rectangular or circular active layer, a layer having a different thermal expansion coefficient or a semiconductor layer having a lattice constant different from that of the active layer is asymmetric with respect to the shape of the active layer. A surface-emitting device having a shape.