JPS5846876B2 - Method for manufacturing gallium phosphide light emitting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention utilizes gallium phosphide (GaP), which has high luminous efficiency.
) The present invention relates to a method for manufacturing a light emitting device.

In general, it is well known that in a GaP light emitting device, red light emission can be obtained by doping a GaP crystal having a pn junction with required amounts of zinc and oxygen, and green light emission can be obtained by doping nitrogen.

Hereinafter, taking a GaP green light emitting device as an example, a conventional example of its manufacturing method will be explained with reference to the vertical cross-sectional view shown in FIG.

Liquid Enca
-psulation Czochrals'ki M
An n-type GaP crystal substrate 1 (hereinafter abbreviated as n-type GaP LEC substrate) prepared using a method (method) and a GaP crystal growth solution doped with sulfur or tellurium as an n-type impurity were paired at a temperature of 1000°C to 1100°C. When the n-type GaP crystal growth solution is cooled at a predetermined cooling rate, the n-type GaP LEC substrate 1 is
Type GaP liquid phase epitaxial growth crystal 2 (Liquid
A Phase Epitajg crystal (hereinafter abbreviated as LPE crystal) grows.

Next, this n-type LPE crystal 2 and a crystal growth solution doped with a p-type impurity such as zinc are heated at a temperature of 1000°C to 110°C.
The p-type LPE crystal 3 is grown by making them face each other at 0°C.

In this way, the n-type LPE crystal 2 and the p-type LPE crystal 3
A pn contact crystal 4 is formed at the junction surface with.

When producing a GaP green light emitting device using this pn junction 4, nitrogen doping is performed during liquid phase epitaxial growth of the n-type GaPLPE crystal 2 in order to increase the concentration of green light emitting centers that contribute to light emission.

However, in such a method, as is well known, the n-type GaP LEC substrate 1 contains more impurities such as silicon and oxygen than crystals formed by liquid phase epitaxial growth. Since many defects are included, the n-type GaPLPE crystal is formed by liquid phase epitaxial growth method by bringing the n-type GaPLEC substrate 1 and the n-type GaP crystal growth solution into contact with each other at a high temperature of 1000°C to 1100°C. 2, n-type GaPLEC
In view of the above-mentioned drawbacks, the present invention has the drawback that impurities such as silicon and oxygen as well as defects are introduced into the substrate 1, making it difficult to create a GaP light emitting device with high luminous efficiency. between an n-type (or p-type) GaP IJC substrate and an impurity-doped n-type (or p-type) Gap LPE crystal.
Liquid phase epitaxial growth is performed at low temperature so that a low concentration n-type (or p-type) LPE crystal is present, and the GaP
It is an object of the present invention to prevent impurities, defects, etc. contained in the LEC substrate from being introduced into the GaP LPE crystal doped with the impurities.

Hereinafter, an embodiment of the method for manufacturing a GaP green light emitting device according to the present invention will be described with reference to longitudinal sectional views shown in FIGS. 2a"-c, respectively.

FIG. 2a shows the state after the process of FIG. 1.

In this first step, on the n-type GaP LEC substrate 1,
Undoped n-type Ga as the first gallium phosphide crystal layer with a required thickness of impurity concentration I XI 016 cm-3 or less
The P LPE crystal 5 is grown by liquid phase epitaxial growth in a hydrogen gas atmosphere under conditions of a crystal growth start temperature and a cooling rate of, for example, 850° C. and 0.5° C./min, respectively.

At this time, there is no problem even if a trace amount of ammonia gas is included in the hydrogen gas atmosphere.

Figure 2 shows the state after the second step.

In this second step, the undoped n-type GaP LP
The n-type GaPLPE crystal 2, which is a second gallium phosphide crystal layer doped with tellurium or sulfur as an n-type impurity and has an impurity concentration of 2×10 17 ctn-3, is placed on the E crystal 5, and the n-type GaPLPE crystal 2 is doped with tellurium or sulfur as an n-type impurity. Liquid phase epitaxial growth is performed by slowly cooling the crystal from a crystal growth starting temperature of 100° C. in an atmosphere of hydrogen gas containing a trace amount of ammonia gas required for doping.

During the liquid phase epitaxial growth of the n-type GaP LPE crystal 2, the undoped n-type GaPLPE crystal 5 prevents impurities and defects contained in the n-type GaP LEC substrate 1 from being introduced into the n-type GaP LPE crystal 2. This can be prevented by

FIG. 2C shows the state after the third step that follows.

In this third step, a p-type GaPLPE crystal 3, which is a third gallium phosphide crystal layer doped with zinc and having an impurity concentration of 1×10 18 ctn-3, is placed on the n-type GaP LPE crystal 2 at a crystal growth starting temperature. 98
Slowly cooled from 0°C to liquid phase epitaxial growth to form n-type G
A pn junction 4 required for producing a green GaP light emitting device is formed at the junction surface between the aP LPE crystal 2 and the p-type GaPLPE crystal 3.

When a green GaP light emitting device is manufactured from the crystal thus formed, as mentioned above, n-type GaP L
Since almost no impurities or defects contained in the n-type GaP LEC substrate 1, which adversely affect the luminous efficiency of the green GaP light emitting element, are introduced into the PE crystal 2, the luminous efficiency of the green GaP light emitting element is 0. 1 to 0.2%,
Compared to the luminous efficiency of green GaP light-emitting devices manufactured using conventional methods, which was approximately 0.02 to 0.05%, green GaP light-emitting devices with luminous efficiency 4 to 10 times higher are now available with good reproducibility. can be manufactured.

In the method of the above embodiment, the impurity concentration of the undoped n-type GaPLPE crystal 5 was set to 1 x 1016 cm-3, and the crystal growth start temperature was set to 850°C, but the present invention is not limited to this. The crystal growth start temperature is also 950°C, which is lower than the crystal growth start temperature of the impurity-doped n-type GaP LPE crystal 2, which is 1ooo°C.
The following is sufficient.

As mentioned above, the method of forming the pn junction 4 of the green GaP light emitting device on the undoped n-type GaPLPE crystal 5 by the dual liquid phase epitaxial growth method was described, but this pn junction 4 can be formed using the n-type GaP LPE crystal A p-type wave diffusion layer is formed on 2 by a diffusion method, and this p-type wave diffusion layer and n
There is no problem even if it is formed with type GaP LPE crystal 2,
Furthermore, although the method for manufacturing a green GaP light emitting device has been described so far, it goes without saying that the method according to the present invention is not limited to this and can also be applied to a method for manufacturing a red GaP light emitting device.

As detailed above, in the method for manufacturing a gallium phosphide light emitting device according to the present invention, n-type (or p-type) G
After forming a first n-type (or p-type) GaP crystal layer with a low impurity concentration on an aP crystal substrate at low temperature, a second n-type (or p-type) GaP crystal layer and a p-type (or n type)
Since the 30th GaP crystal layer is created to form a pn junction, impurities and defects contained in the GaP substrate are removed.
Since the introduction into the 20th GaP crystal layer can be prevented, compared to conventional methods, it is possible to obtain a variable element with a p-n junction that has fewer impurities and defects that cause non-radiative recombination centers. As a result, a light emitting element with high luminous efficiency can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view showing a conventional method for manufacturing a GaP green light emitting device, and FIGS.
FIG. 2 is a longitudinal cross-sectional view showing an example of a method for manufacturing a P-green light emitting device. In the figure, 1 is an n-type GaP LEC substrate, 2 is an n-type GaP LPE crystal doped with n-type impurities, 3 is a p-type GaP LEP crystal doped with p-type impurities, 4 is a p-n junction surface, and 5 is a low concentration An undoped n-type GaPLPE crystal is shown. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1. On an n-type (or p-type) gallium phosphide crystal plate,
A step of forming an n-type (or p-type) first gallium phosphide crystal layer with a low impurity concentration by a liquid phase epitaxial growth method; forming a second gallium phosphide crystal layer (or p-type) by liquid phase epitaxial growth; and forming a third p-type (or n-type) gallium phosphide crystal layer on the second gallium phosphide crystal layer. phosphide, comprising the step of forming a layer, and setting the crystal growth start temperature of the first gallium phosphide crystal layer to a lower temperature than the crystal growth start temperature of the second gallium phosphide crystal layer. A method for manufacturing a gallium light emitting device. 2. The method of manufacturing a gallium phosphide light emitting device according to claim 1, wherein the third gallium phosphide crystal layer is formed by a liquid phase epitaxial growth method. 3. A method for manufacturing a gallium phosphide light emitting device according to claim 1, characterized in that the third gallium phosphide crystal layer is formed by an impurity diffusion method.