JPH04266074A - Manufacture of phosphor gallium phosphide green light-emitting element - Google Patents

Abstract

PURPOSE:To obtain a gallium phosphide green light-emitting element with an improved light-emitting efficiency with an improved reproducibility under stable condition. CONSTITUTION:After an n-type gallium phosphide layer and a p-type gallium phosphide layer are subjected to epitaxial growth in sequence on an n-type gallium phosphide substrate, donor impurities of the n-type gallium phosphide layer can be compensated for by diffusion of zinc by performing heat treatment while mainaining a temperature 12 of 300 deg.C-650 deg.C and a donor concentration of pn junction of the n-type gallium phosphide layer can be reduced, thus obtaining a gallium phosphide green light-emitting element with an improved light-emitting efficiency under stable conditions with an improved reproducibility.

Description

[Detailed description of the invention]

[Purpose of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a gallium phosphide green light emitting device.

0002

[Prior Art] Conventionally, gallium phosphide green light emitting devices (G
aP green light-emitting elements) are used as light sources for high-intensity lamps, outdoor display signboards, and the like. And this GaP
For example, the configuration of the green light emitting element has a chip size of 0.3
It is mm square, has a cross-sectional configuration as shown in FIG. 3, and has a total thickness of 300 μm. This consists of an n-type gallium phosphide (GaP) layer 2 doped with tellurium (Te) that is layered on an n-type gallium phosphide (GaP) substrate 1.
On this n-type GaP layer 2, an n+ type G layer with a thickness of 20 μm is formed.
An aP layer 3 and an n- type GaP layer 4 with a thickness of 15 .mu.m are successively deposited, and a p-type GaP layer 5 with a thickness of 20 .mu.m is further deposited on the n--type GaP layer 4. Note that a p-side electrode 6 is provided on the upper surface of the p-type GaP layer 5, and two n-side electrodes 7 are provided on the lower surface of the n-type GaP substrate 1. A light emitting region is formed near the pn junction 8 of the n- type GaP layer 4.

Such a gallium phosphide green light emitting device (
The manufacturing method for GaP green light emitting device is generally n-type GaP
On the substrate 1 or on the n-type GaP layers 2 and 3 provided on the n-type GaP substrate 1, an n- type GaP layer 4 and a p-type GaP layer 5 are successively deposited by liquid phase epitaxial growth. A light emitting region is formed in the vicinity of the pn junction 8 of the - type GaP layer 4 by doping nitrogen, which is a light emitting center. Liquid phase epitaxial growth and nitrogen doping are usually performed in a predetermined growth furnace equipped with a quartz reaction tube, with the n-type GaP substrate 1 placed in a quartz boat.

[0004] Furthermore, the light emitting region of the GaP green light emitting device is
It is formed near the pn junction 8 of the n- type GaP layer 4, and the luminous efficiency can be improved by lowering the donor concentration in this region to improve the electron injection efficiency. Empirically, the donor concentration in the emission region is 0
．． It is said that the optimum value is 4 to 1.5×10 16 /cm 3 .

Therefore, in order to lower the donor concentration of the n- type GaP layer 4, silicon (Si), which is present in large quantities in the reaction environment, is reduced by using a board or a reaction tube during manufacturing.
Ammonia gas (NH3
) is used. That is, doping with nitrogen is carried out by making the atmosphere a NH3-added gas atmosphere when epitaxially growing the n-type GaP layer 4, and at this time Si reacts with the added NH3 to form silicon nitride. (Si3 N4) is formed. As a result, Si, which becomes a donor, is transferred to the n- type GaP layer 4.
It becomes a form that is not incorporated into the crystal of n- type GaP.
The donor concentration in layer 4 will be low. However, with such a method, it is not possible to sufficiently reduce the donor concentration with good reproducibility, and the donor concentration is reduced to at most 2.0×10 16 /cm 3 , making it impossible to obtain an optimal value.

Furthermore, by increasing the amount of NH3 added,
If an attempt is made to reduce the donor concentration by excessively reacting H3 and Si, the amount of Si3 N4 grown increases, and this causes abnormal growth of the n- type GaP layer 4. In other words, there are parts that grow and parts that do not grow in the n- type GaP layer 4, and there are local differences in the thickness of the resulting layer, making it impossible to maintain the flatness of the top surface, and also making it difficult to maintain uniform properties of the upper layer to be formed. cannot be made into something.

As described above, the donor concentration in the light emitting region formed in the n- type GaP layer 4 cannot be made sufficiently low under stable conditions, making it difficult to improve the light emitting efficiency.

[0008]

[Problems to be Solved by the Invention] The present invention has been made in view of the above-mentioned situation in which it is difficult to improve luminous efficiency.
The purpose is to provide a method for manufacturing a gallium phosphide green light emitting device that can produce a gallium phosphide green light emitting device with improved luminous efficiency with good reproducibility under stable conditions.

[Configuration of the invention]

0010

[Means for Solving the Problems] A method for manufacturing a gallium phosphide green light-emitting device of the present invention includes forming at least one layer of n-type gallium phosphide on an n-type gallium phosphide substrate by liquid phase epitaxial growth.
This method is characterized by sequentially forming a type gallium phosphide layer and a p-type gallium phosphide layer, followed by heat treatment while maintaining the layer in an atmosphere at a temperature of 300°C to 650°C.

[0011]

[Function] The method for manufacturing the gallium phosphide green light emitting device constructed as described above is based on
The heat treatment is carried out by maintaining the temperature at a temperature of 650°C to 650°C. Therefore, zinc in the p-type gallium phosphide layer is diffused into the n-type gallium phosphide layer where the light-emitting region is formed, and becomes a donor for this layer. This compensates for impurities, and the donor concentration of the pn junction of the n-type gallium phosphide layer can be sufficiently reduced. This makes it possible to easily obtain a gallium phosphide green light-emitting element with improved luminous efficiency through simple steps.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram schematically showing the temperature in the manufacturing process, and FIG. 2 is a diagram showing the improvement rate of luminous efficiency. In the figure, 10 is the temperature of the growth furnace of the liquid phase epitaxial growth apparatus, 11 is the temperature of the vaporization furnace, and 12 is the temperature of the heat treatment furnace. In addition, when explaining, the parts corresponding to FIG. 3 showing the configuration of the GaP green light emitting device are as follows.
The explanation will be given by attaching the corresponding symbol.

First, in manufacturing a GaP green light emitting device, gallium (Ga), gallium phosphide polycrystalline (Ga
An n-type GaP substrate 1 on which an n-type GaP layer 2 doped with tellurium (Te) is layered on the upper surface of
Each horizontal slide boat made of quartz is installed in a predetermined storage recess, and this slide boat is installed in a furnace of a liquid phase epitaxial growth apparatus.

After installing the slide boat in the growth furnace,
The inside of the furnace was replaced with a vacuum, and while hydrogen gas (H2) was flowing at a flow rate of 2 liters per minute, the temperature inside the furnace was raised to 10% at the normal heating rate.
Heat up to about 00°C. After raising the temperature, the inside of the furnace was heated to 1000
℃ for 90 minutes, an epitaxial solution such as Ga is brought into contact with the upper surface of the n-type GaP layer 2 on the n-type GaP substrate 1, and the substrate is left in this state for another 60 minutes. Next, the temperature inside the growth furnace is lowered at a cooling rate of, for example, 2°C/min.
While cooling the n-type GaP substrate 1 to 970°C,
A GaP layer 3 is epitaxially grown on the upper surface of the type GaP layer 2. This GaP layer 3 is made of quartz and H2 of the slide boat.
Due to the reaction of the gas, Si (which becomes a donor) dissolved in the Ga solution is doped to form an n+ layer.

[0015] When the temperature inside the growth furnace reaches 970°C, while maintaining this temperature, the atmosphere inside the growth furnace is changed to a gas atmosphere to which ammonia gas (NH3) is added, for example, a mixture of argon gas (Ar) and NH3. Create a mixed gas and maintain this state for 100 minutes. Then, check the temperature inside the furnace again.
From 970℃, for example, at a cooling rate of about 2℃/min 930
The n- type GaP layer 4 is grown while cooling to .degree. At this time, since NH3 is added to the atmospheric gas, the Si dissolved in the Ga solution reacts with NH3 to form Si3N4, and the growing n-type G
It is no longer taken into the aP layer 4. Therefore, the donor concentration of the n-type GaP layer 4 grown at this time is reduced to about 2.0×10 16 /cm 3 .

Next, when the furnace temperature reached 930°C, the growth furnace was maintained in this state, and on the other hand, zinc (Z
n) Start the operation of the vaporizing furnace and raise the temperature inside the furnace. Zn is evaporated by this temperature increase, and this evaporated Zn is
Pour onto a slide boat in a growth furnace maintained at °C. When the temperature of the Zn vaporization furnace reached 720°C and became stable, the supply of NH3 to the growth furnace was stopped, the atmosphere gas in the furnace was changed from a mixed gas of Ar and NH3 to a gas atmosphere containing only Ar, and the temperature of the vaporization furnace was The reactor is operated in parallel with the growth reactor while maintaining the temperature at 720°C. The growth furnace also maintains the temperature inside the furnace even after changing the gas atmosphere.
Maintain the temperature at 930°C, and after 100 minutes, e.g.
Cooling is carried out at a rate of temperature drop of about 0.degree. C./minute to 750.degree. C., and then the operation of the growth furnace is stopped and the temperature inside the furnace is allowed to cool down naturally to room temperature over 6 to 10 hours. At the same time, the vaporizer is also in the process of cooling down, and the temperature of the growth furnace is decreasing.
When the temperature reaches 800°C, the operation is stopped and the temperature inside the furnace is lowered by natural cooling. During the cooling process of the growth furnace, a p-type GaP layer 5 is epitaxially grown on the upper surface of the n-type GaP layer 4. As a result, an n- type GaP layer 4, a p-type GaP layer 5, etc. are sequentially formed on the n-type GaP substrate 1, and an epitaxial wafer having a pn junction 8 of the n- type GaP layer 4 where a light emitting region is formed is obtained. .

Further, the obtained epitaxial wafer is placed in a heat treatment furnace, and the temperature is raised to 500° C. under normal pressure with Ar atmosphere in the furnace. Then the inside of the furnace is heated to 500℃
After maintaining the temperature for 10 hours, the temperature inside the furnace is lowered to room temperature and the epitaxial wafer is heat-treated.

Then, predetermined p-side electrodes 6 and n-side electrodes 7 are formed on both sides of the heat-treated epitaxial wafer,
A GaP green light emitting device is obtained in the form of a 0.3 mm square chip.

The GaP green light emitting device obtained in this example described above was compared with one formed by a conventional manufacturing method. In addition, for those formed by the conventional manufacturing method, an epitaxial wafer that was epitaxially grown in a growth furnace under the same conditions as in this example was used without further heat treatment at 500°C for 10 hours.
This is a GaP green light emitting device obtained as a 0.3 mm square chip.

According to this, the donor concentration of the n- type GaP layer 4 obtained in this example is 1.0 to 1.5.
x 1016/cm3, which satisfies the optimum donor concentration of 0.4 to 1.5 x 1016/cm3, and the donor concentration of the conventional method is 2.0 to 3.0. ×1016/cm3, this was a much improved value. Furthermore, the luminous efficiency obtained by the present invention showed a high value, showing an average improvement rate of about 50% compared to that obtained by the conventional method.

Further, in the above embodiment, the epitaxial wafer that had been epitaxially grown in the growth furnace was placed in a heat treatment furnace and kept at a temperature of 500°C for 10 hours for heat treatment, but the temperature in the furnace was lowered to 300°C. From 700
When we looked at the improvement rate of luminous efficiency by varying the temperature within the temperature range, Figure 2
As shown with the heat treatment temperature on the horizontal axis and the rate of improvement in luminous efficiency on the vertical axis, the luminous efficiency is improved over the conventional luminous efficiency in the range of 300°C to 650°C. In addition, especially in the range of 400℃ to 600℃, the average improvement rate exceeds 40%,
This is a significant improvement.

The reason why the luminous efficiency improves in the range of 300° C. to 650° C. and does not improve at other heat treatment temperatures is considered to be due to the following reasons. That is, in the range of 300°C to 650°C, Zn in the p-type GaP layer 5 diffuses into the n- type GaP layer 4, and
Since donor impurities in the - type GaP layer 4 are sufficiently compensated for, the donor concentration near the pn junction can be further reduced. In addition, at a temperature lower than 300°C, Zn in the p-type GaP layer 5 diffuses into the n-type GaP layer 4 less, and the donor concentration in the n-type GaP layer 4 does not decrease. In the case of a high temperature exceeding This is thought to be due to deterioration.

As described above, according to this embodiment, compared to the conventional manufacturing method, after epitaxial growth, only 30
This method is simple and can be carried out under stable conditions by simply performing heat treatment in the range of 0°C to 650°C, which allows formation of good properties for each layer and improves luminous efficiency with good reproducibility. Furthermore, separate from performing crystal growth in a liquid phase epitaxial growth apparatus, heat treatment can be performed in a heat treatment furnace to improve luminous efficiency,
This makes it possible to improve luminous efficiency with good mass productivity.

[0024] In the above embodiment, after epitaxial growth is performed, the next heat treatment is performed after being naturally cooled to room temperature, but if epitaxial growth is performed, the temperature should not be returned to room temperature. The following heat treatment may be performed, and there is no need to provide a heat treatment furnace separate from the liquid phase epitaxial growth apparatus, etc., and the present invention can be implemented with appropriate modifications within the scope of the gist. .

[0025]

[Effects of the Invention] As is clear from the above explanation, the present invention is effective at heating temperatures of 300°C to 650°C after epitaxial growth.
By employing a structure in which the heat treatment is performed while maintaining the temperature at , it is possible to obtain a gallium phosphide green light-emitting element with improved luminous efficiency with good reproducibility under stable conditions.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing temperatures during a manufacturing process in an embodiment of the present invention.

FIG. 2 is a diagram showing the improvement rate of luminous efficiency according to the example of FIG. 1;

FIG. 3 is a cross-sectional view showing an example of a gallium phosphide green light-emitting device.

[Explanation of symbols]

4 n-type GaP layer 5 p-type GaP layer 8 pn junction 10 Temperature of growth furnace 11 Temperature of vaporizer 12 Temperature of heat treatment furnace

Claims (1)

[Claims] Claim 1: After sequentially forming at least one n-type gallium phosphide layer and a p-type gallium phosphide layer on an n-type gallium phosphide substrate by liquid phase epitaxial growth, in an atmosphere at a temperature of 300°C to 650°C. A method for manufacturing a gallium phosphide green light-emitting device, which comprises holding the gallium phosphide green light-emitting device in a heat-treated state.