JPH04320070A - Light emitting element - Google Patents

Abstract

PURPOSE:To obtain a light emitting element having excellent characteristics such as high emitting efficiency of a light, etc., by forming semiconductor layers having different lattice constants and thermal expansion coefficients on a semiconductor substrate, and reducing a dislocation for disturbing an operation of the element and a strain stress for increasing and propagating the dislocation when the element such as a light emitting diode, etc., is manufactured. CONSTITUTION:A GaAs/AlGaAs-based double hetero structure is formed on an n-type Si substrate 1 through a selectively etched layer 3. Then, an etching groove 9 from an SiO2 layer 8 to the layer 3 is formed, only part of the layer 3 is removed by etching by using the groove 9, and a light emitting region is so formed as to oppose in a state separated from the substrate. Thereafter, the double hetero layer is thermally annealed. Eventually, a p-type AuZn 10 is formed only on the periphery of the element by using a mask of the SiO2, an n-type Au-Sb ohmic electrode 11 is formed on a rear surface of the substrate, and the element is separated to form a light emitting diode.

Description

[Detailed description of the invention]

0001

[Industrial Field of Application] The present invention relates to semiconductor light emitting devices such as light emitting diodes, laser diodes, and optical ICs. In particular, the present invention relates to semiconductor light emitting devices such as light emitting diodes, laser diodes, and optical ICs. When a light emitting device is formed by heteroepitaxial growth, various defects and strain stress based on the lattice constant and thermal expansion coefficient are reduced and eliminated, and the structure of the light emitting device has good characteristics.

0002

[Prior Art] In recent years, for example, when forming GaAs semiconductor devices, Si
GaAs is grown on the substrate by heteroepitaxial growth.
A method of forming a semiconductor crystal layer has been attempted, and attempts have also been made to fabricate light emitting diodes and the like using the GaAs semiconductor crystal layer obtained by this method.

0003

However, the life of the light emitting diode obtained by the above method is short and the luminous intensity is low.

The main reason for this is that a large number of dislocations occur in the GaAs semiconductor crystal layer due to the difference in lattice constant and thermal expansion coefficient between the GaAs semiconductor crystal and the Si semiconductor crystal substrate, and the dislocations occur during the operation of the device. This is strain stress that can propagate and multiply in the active layer.

The present invention aims to further reduce the dislocation density and strain stress of this epitaxially grown layer, and to obtain a light-emitting element with good characteristics in which the efficiency of extracting light in the upward direction is improved.

[0006]

[Means for Solving the Problems] A light emitting device of the present invention for solving the above problems is formed on a semiconductor substrate and has a lattice constant and a coefficient of thermal expansion that are different from those of the semiconductor substrate. In a light-emitting element made of a semiconductor layer, the light-emitting region of the light-emitting element is formed so as to face the light-emitting region at a distance from the semiconductor substrate surface, and the upper ohmic electrode of the light-emitting element has a light-emitting region near the bottom of the light-emitting element. Only the peripheral portion of the light emitting element is provided so that the region faces the semiconductor substrate in a spaced manner, and the light emitting element and the semiconductor substrate are bonded only at the center portion.

[0007]

[Operation] According to the present invention described above, many dislocation portions existing near the interface due to the difference in lattice constant are removed, and dislocations in the light emitting region are reduced without multiplication of dislocations from near the interface. Can be done. Furthermore, since the strain stress caused by the difference in thermal expansion coefficients is alleviated, the propagation and propagation of these dislocations into the light emitting region due to strain stress is also reduced, resulting in a good structure with few dislocations and strain stress that impede the operation of the device. A light emitting element with characteristics can be obtained. Furthermore, when considering light emission in the upward direction, the current flows from the periphery to the center, so the light emitting area spreads from directly under the electrode to the center, and the proportion of light shielded by the electrode decreases. Since the substrate is not in contact with the semiconductor layer, the light emitted downward is effectively reflected upward by the semiconductor layer-air interface without being absorbed by the substrate, resulting in good emission efficiency.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

First, as shown in FIG. 2, a 250 μm thick n
0 on a Si substrate 1 using a conventionally known two-step growth method.
．． An n-type GaAs layer 2 having a thickness of 2 μm is formed. Furthermore, epitaxial growth is possible with GaAs, and selective etching is possible with respect to GaAs.
For example, a selective etching layer 3 of n-type Al0.7Ga0.3As is formed to a thickness of 0.5 μm. On the selective etching layer 3, a conventionally known GaAs/AlGaAs double heterostructure semiconductor crystal layer (1.5 μm thick n-type Al0.3
It consists of a Ga0.7As layer 4, an n-type GaAs layer 5 with a thickness of 0.2 μm, and a p-type Al0.3Ga0.7As layer 6 with a thickness of 1.5 μm. ) is epitaxially grown. Furthermore, a p-type GaAs layer 7 and a SiO2 layer 8 having a thickness of 0.2 μm are formed thereon.

Next, an annular groove 9 is formed by etching that reaches the selective etching layer 3 from the surface of the SiO2 layer. After that, using the cut groove 9, Al0
．． Only the 7Ga0.3As selective etching layer 3 was partially removed by etching, and FIG. 3 is a plan view, and FIG.
As shown in the cross-sectional view taken along line A', a light-emitting region portion is obtained in which only the central portion is joined to the Si substrate 1 and the periphery is partially separated from the Si substrate 1. In this state, known thermal cycle annealing is performed to reduce dislocations in the separated active layers. As a result of evaluating the strain in the vicinity of the GaAs light emitting regions partially separated in such a shape by computer simulation and photoluminescence measurement, it was found that the strain was relaxed to less than half of that before the separation. Regarding dislocations, an examination of etch pits caused by molten KOH revealed that the number of dislocations had decreased, and that there were regions in which almost no dislocations were observed, especially near the edges.

Finally, as ohmic electrodes, an Au--Zn electrode 10 is deposited on the outer periphery of the upper surface of the SiO2 layer 8, and an Au--Sb electrode 11 is deposited on the lower surface of the Si substrate 1 to form an alloy. As shown in FIG. 3, the ohmic electrode on the top surface is formed around the periphery of the element, and the other butt parts and the like are blocked by SiO2. Thereafter, elements are separated using cleavage or the like to complete the light emitting diode. Annealing may be performed after electrode formation within a range that does not adversely affect the ohmic electrode.

0012

According to the present invention, even when manufacturing a light emitting device by forming semiconductor layers having different lattice constants and coefficients of thermal expansion on a semiconductor substrate, a light emitting region with low dislocation density and low strain stress can be created. Furthermore, a light-emitting element with good characteristics such as high emission efficiency can be obtained.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a light emitting device according to an embodiment of the present invention.

[Figure 2] Cross-sectional view of one manufacturing process of the same example

[Figure 3] Plan view of one manufacturing process of the same example

[Explanation of symbols]

1 n-type Si substrate 2 n-type GaAs layer 3 n-type Al0.7Ga0.3As selective etching layer 4 n-type Al0.3Ga0.7As cladding layer 5 n-type GaAs active layer 6 p-type Al0.3Ga0.7As cladding layer 7
P-type GaAs layer 8 SiO2 layer 9 Etching groove 10 Au-Zn electrode 11 Au-Sb electrode

Claims (1)

[Claims] 1. A light emitting element formed on a semiconductor layer formed on a semiconductor substrate and having a lattice constant and thermal expansion coefficient different from those of the semiconductor substrate, comprising:
removing the interface between the semiconductor layer and the semiconductor substrate from the surroundings;
The upper ohmic electrode has only the peripheral part of the surface, and the part near the bottom of the electrode that becomes the light emitting area is formed so as to face away from the semiconductor substrate, and only the center part is bonded to the semiconductor substrate. Characteristic light-emitting elements.