JPS6048915B2 - Injection type light emitting semiconductor device and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an injection type light emitting semiconductor device that can emit light in response to an injection current, and a method for manufacturing the same.

In recent years, GaA1As has attracted attention as a semiconductor material for red light emitting elements with high efficiency and good current-light output linearity.

The Ga, -xA]xAs material has a direct transition type band structure from X=0 to around 0.4, and is useful as a material for a light emitting device with a wavelength of 0.6 to 0.9 μm.

Conventionally, the structure of a light-emitting device using this material is to layer a GaAIAs layer with a forbidden band width corresponding to the emission wavelength on top of a GaAIAs layer with a wider forbidden band width so as to be transparent to this wavelength.
By changing the wavelength of the AIAs layers and making the conductivity types of these layers different from each other, a PN junction is obtained and a light emitting device is obtained. In such a structure, the heterojunction surface with different forbidden band widths and the P-N junction surface with different conduction types coincide, so the P-N junction surface has different conductivity types.
The band structure near the N junction has a discontinuous shape with spikes 4 and notches 5 as shown in FIG. In addition, the first
In the figure, 3 is a P-N junction surface and a heterojunction surface, 1
indicates a P-type semiconductor layer, and 2 indicates an N-type semiconductor layer.

When an electric field is applied to this diode, the notch 5 acts as a trap, so that light different from the main wavelength of light emission is generated, which deteriorates the light emission spectrum and lowers the light emission efficiency. Further, due to the effects of the spikes 4 and notches 5, a switching phenomenon appears in the current-voltage characteristics, which impedes light emission with good reproducibility. Therefore, in order to improve luminous efficiency and stabilize current-voltage characteristics, it is desired to manufacture a device without discontinuities at the PN junction. The present invention aims to separate the P-N junction and the heterojunction, and eliminate discontinuous connections in the vicinity of the P-N junction.

This will be explained below by giving examples. FIG. 2 shows a cross section of an injection type light emitting device 10 according to the present invention.

The element 10 is constructed on a single crystal substrate 11 of conductivity type P-type GaAs. The typical thickness of the GaAs substrate 11 is 150μ
m, Zn as an acceptor is 1×10'° atomic number α
Including around −°. GaAlAs layers 12, 13, and 14 are grown on the substrate 11 using a liquid phase epitaxial growth method. The amount of layer 12 varies depending on the desired emission wavelength. In a typical example, GaO is used to obtain an emission wavelength of 0.66 μm.
．． . 5AlO. 3. Grow AS to about 25 μm.

The conductivity type is P type, and Zn is about 1×1 as an acceptor.
The layers 13 and 14 are made of GaO.

AlO. Since it is made of 8As and is transparent to the above emission wavelength, it serves as a light extraction window. Layer 13 is made of GaO. 2A
lO. Appropriate heat treatment during and after the growth of 8As diffuses the Zn in layer 12, thereby compensating for donor impurities and creating a P-type region. The thickness of the layer 13 must be thinner than the diffusion distance of the minority carrier electrons, since electron-hole coupling must occur within the region of the layer 12. The heat treatment to obtain this thickness was performed at a temperature of 3
If you do it for about 0.1 to 3 hours at a temperature between 00 and 1200℃.
It is possible. In this example, this heat treatment was carried out at a temperature of 800°C.
It lasted two hours.

Layer 14 is 10μ3 thick doped with Te or other suitable donor impurity at a concentration on the order of 1×10″° Cm-° atoms.
m of N-type GaO. 2AlO. It is an 8As layer.

In order to make this element work as a diode, a low resistance N
A GaAs layer 15 is grown by liquid phase epitaxial growth, and an Au-Ge-Ni electrode (negative electrode) 16 is deposited and alloyed to obtain ohmic contact. Since the GaAs layer 15 and the negative electrode 16 interfere with extraction in the Z direction, they are formed into an appropriate size and shape by selective etching technology. Positive electrode 17
evaporate and deposit Au-Zn to obtain ohmic contact, and fix it to the supporting metal jig 19 using paste 18. Negative electrode 1
If a lead wire 20 of Au wire is taken out from 6 and a circuit is constructed between it and the metal support 19 using a battery or other method, the element 10 will emit light at the desired wavelength. The PN junction surface 21 of the element 10 is the interface between the layers 13 and 14, and the heterojunction surface 22
is the interface between layer 12 and layer 13. This results in a band structure as shown in FIG. 3, and separation of the PN junction surface 21 and the heterojunction surface 22 is achieved. Make this element emit light
By doing so, an optical output approximately m times greater than that of a conventional element in which the heterojunction surface and the PN junction surface coincide with each other was obtained. Also, the switching characteristics of voltage-current characteristics were no longer observed.
Although the present invention has been described in detail with reference to one embodiment, it is possible to use a Group 2 acceptor impurity such as Cd in place of Zn.

Furthermore, the light-emitting material is not limited to GaAlAs-based materials, and other semiconductor materials can be used.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the energy band structure of a conventional injection type light emitting semiconductor device, FIG. 2 is a sectional view of a semiconductor device according to an embodiment of the present invention, and FIG. 3 is a schematic diagram of the energy band structure of the same embodiment. It is a diagram. 11... P-type GaAs single crystal substrate, 12...
...P-type GaO. 5AlO. 35AS) 13...
...P-type GaO. 2AlO. 8AS) 14...
N-type GaO. 2AlO. 8AS) 15...N-type GaAs epitaxial layer, 16...Au-G
e-Ni electrode (negative electrode), 17...Au-Zn
Electrode (positive electrode), 21...P-N junction surface, 22
・・・Heterojunction surface.

Claims (1)

[Claims] 1. In an injection type light emitting semiconductor device made of a semiconductor having two or more different forbidden band widths and at least one PN junction, the surface of the first semiconductor layer which is the main light emitting region The second semiconductor layer has a wider forbidden band width than the semiconductor layer, has the same conduction type, and has a thickness thinner than the diffusion length of the minority carriers.
a third semiconductor layer having a conduction type different from that of the second semiconductor layer on the surface of the second semiconductor layer and having the same forbidden band width as the second semiconductor layer; An injection type light emitting semiconductor device characterized by having the following. 2. A semiconductor layer having an N-type conductivity type and having a wider forbidden band width than the first semiconductor layer is grown on the surface of the first semiconductor layer of the P-type conductivity type using zinc or cadmium as an acceptor, and then heat-treated. The acceptor impurity is diffused from the heterojunction surface toward the N-type semiconductor layer, thereby forming a second semiconductor layer having P-type conductivity within the N-type semiconductor layer and preventing the diffusion from reaching the second semiconductor layer. A method for manufacturing an injection type light emitting semiconductor device, characterized in that an N-type semiconductor layer is used as a third semiconductor layer.