JPH04328823A - Manufacture of epitaxial wafer for light emitting diode - Google Patents

Abstract

PURPOSE:To manufacture nitrogen atom containing GaAs1-xPx epitaxial wafers having high quality PN junction within a relatively short time. CONSTITUTION:In order to vapor phase epitaxial growth a GaAs1-xPx (0.4<=x<=0.9) having PN junction on a GaP single crystal substrate, the partial pressure of Ga component and that of phosphorus and arsenic components during the epitaxial growth step of a nitrogen atom containing N-type Ga1-xPx are specified to be 0.003 or 0.02atm while the partial pressure of Ga component and that of phosphorus and arsenic components during the epitaxial growth step of nitrogen atom containing P-type GaAs1-xPx are specified to be 0.01 or 0.05atm. Thus, a P-type layer in sufficient thickness for efficiently emitting the light inside a crystal can be grown meeting the requirement for small diffusion. Through these procedures, the light emitting diode in orange, yellow color, etc., having almost the same luminance for the outdoor application as that of the lilght emitting diode manufactured using the crystal grown by a liquid phase process can be manufactured within a relatively short time.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to GaAs1-XPX (here, 0.4≦x≦0) suitable for manufacturing light emitting diodes.
．． 9) Regarding a method for manufacturing an epitaxial wafer.

0002

[Prior Art] Conventionally, light emitting diodes made of GaAs1-XPX can emit light in various colors from infrared light to green light by changing the mixed crystal ratio x. N-type GaAs doped with sulfur
By adding nitrogen, which acts as an isoelectronic trap, to 1-XPX, it is possible to emit light in intermediate colors such as orange and yellow, so it is widely used as a display element.

[0003] When manufacturing such epitaxial wafers, a grading layer with a mixed crystal ratio x varying from 1 to a desired mixed crystal ratio is usually formed on the GaP substrate, thereby controlling the lattice constant. This allows the growth of epitaxial crystals with lattice constants that do not match that of the crystal substrate. Then, a relaxation layer is provided on this grading layer to alleviate defects occurring in this grading layer,
A light emitting layer is deposited on this relaxation layer. GaAs1-XP suitable for orange, yellow, etc. light emitting diodes
Since the X crystal uses a layer containing nitrogen, which is an isoelectronic trap, as a light-emitting layer, this light-emitting layer must contain nitrogen, and in order to make this layer an N-type semiconductor, it is doped with, for example, sulfur. do. Then, by doping zinc, which is a P-type impurity, from the surface of this nitrogen-containing N-type GaAs1-XPX epitaxial wafer using a thermal diffusion method, a PN junction is formed in this light-emitting layer, thereby forming a light-emitting diode. Manufacture epitaxial wafers for the board.

As mentioned above, conventional GaAs1-XPX
When manufacturing epitaxial wafers by vapor phase method, N
A PN junction is formed by epitaxially growing only a type semiconductor and diffusing zinc or the like near the surface. Diameter 5 of resin sealing structure
When it is a light emitting diode of mm, the center emission wavelength is 63
When the wavelength is 0 nm, it is about 220 mcd, and when the center emission wavelength is 580 nm, it is about 250 mcd.

On the other hand, when a PN junction is formed by epitaxial growth using a liquid phase method, it is about 520 mcd when the center emission wavelength is 570 nm using GaP with a mixed crystal ratio x=1, which is suitable for orange, yellow, etc. light emitting diodes. XP
Even if we take into account the difference between the mixed crystal ratio of X crystal X = 0.65 to 0.85 and the above-mentioned GaP where x = 1, the light emitting diode manufactured using the crystal epitaxially grown by the liquid phase method
The brightness of the LED is about 1.5 to 2 times that of a light emitting diode manufactured by the vapor phase method. From research to develop a high-brightness light emitting diode with a PN junction formed using a liquid phase method, for example, in the case of the above central emission wavelength of 570 nm, the recombination rate at the P layer surface, the minority carrier diffusion length with respect to the zinc concentration, The optimal thickness of the P layer based on calculations taking into account the absorption coefficient of the GaAs1-XPX crystal containing zinc, nitrogen, etc. is about 11 μm, and the optimal layer thickness of the P layer based on experiments is about 25 μm. . If the center emission wavelength is 58
In the case of 0 nm, the optimal layer thickness of the P layer based on the calculation is approximately 8 μm, so the optimal layer thickness of the P layer is 1
It can be estimated that about 8 μm is required, but it is practically impossible to perform deep diffusion of about 18 μm while controlling the carrier concentration of the P layer to 10 18 or less.

[0006] For this reason, for example,
The invention described in Publication No. 9 is based on the mixed crystal ratio X= where the layer thickness of the P layer is large.
1 discloses the case where the central emission wavelength is 567 nm, and the growth temperature of the P-type semiconductor is lowered in order to avoid undesirable diffusion of zinc (autodoping) during the growth of the P-type semiconductor. However, due to this drop in growth temperature, the growth rate of the P layer decreases to 0.67 times that of the N layer, and it takes 1.49 times as long to grow the desired layer thickness. Therefore, autodoping cannot be sufficiently suppressed due to this long epitaxial growth time.

[0007]

[Problems to be Solved by the Invention] It is an object of the present invention to obtain a P layer with a carrier concentration of 1018 or less, which has a sufficient thickness to efficiently extract the light emitted from inside the epitaxial wafer crystal, and to form a high-quality PN junction using nitrogen. Contains GaA
It is an object of the present invention to obtain a method for manufacturing s1-XPX epitaxial wafers in a relatively short time.

[0008]

[Means for Solving the Problems] That is, the present invention provides a light emitting method for growing a GaAs1-XPX (here, 0.4≦x≦0.9) single crystal layer having a PN junction on a GaP single crystal substrate by vapor phase epitaxial growth. In a method for manufacturing an epitaxial wafer for a diode, N-type GaAs1 containing nitrogen atoms is used.
- The partial pressure of Ga component and the partial pressure of phosphorus and arsenic components during XPX epitaxial growth is 0.003 to 0.02at.
m, and the partial pressure of Ga component and the partial pressure of phosphorus and arsenic components in P-type GaAs1-XPX epitaxial growth containing nitrogen atoms are set to 0.01 to 0.05 atm.

[0009]

[Function] The partial pressure of Ga component and the partial pressure of phosphorus and arsenic components during epitaxial growth of N-type GaAs1-XPX containing nitrogen atoms are changed to
By changing the partial pressures of the Ga component, phosphorus, and arsenic components during epitaxial growth, a fast growth rate can be achieved while keeping the growth temperature constant during epitaxial growth, and P
It has become possible to manufacture a nitrogen-containing GaAs1-XPX epitaxial wafer with a thick layer and a high-quality PN junction.

0010

[Examples] Examples of the present invention are shown below, but the present invention is not limited thereto.

[0011]

[Example 1] In a vertical quartz reaction tube with an inner diameter of 150 mm and a length of 140 cm, an N-type GaP single crystal substrate was polished and had a thickness of 250 μm and a diameter of 2 inches with a carrier concentration of 5×.
Twelve No. 1017 N-type GaP substrates were installed, and liquid metal gallium was placed in a quartz container upstream in the gas flow direction within the reaction tube. After purging the reaction tube with air for about 30 minutes at a nitrogen gas flow rate of 10 l/min, the hydrogen gas flow rate was set at 6 l/min until the metal gallium reached 830°C and the substrate reached 850°C. Heated in an electric furnace. After that, hydrogen chloride gas to transfer the metal gallium in the quartz container was supplied at 20 cc/min, and hydrogen sulfide gas diluted to 100 ppm with nitrogen gas as an N-type dopant was diluted to 10% with hydrogen gas at 60 cc/min. The phosphine gas diluted with hydrogen gas was introduced into the reaction tubes at a flow rate of 120 cc/min, and together with the phosphine gas diluted with hydrogen gas.
Grading was performed for 90 minutes while increasing 0% arsine gas at a rate of 0 cc/min to 0.73 cc/min to produce an N-type grading layer. When 90 minutes have elapsed for this grading layer generation, the flow rate of the 10% arsine gas diluted with hydrogen gas is 66 cc/min.
Arsine gas was continuously introduced into the reaction tube at a constant rate of 66 cc/min. After the grading layer is formed as described above, in order to alleviate defects in the grading layer, N-type Ga which does not contain nitrogen atoms is grown in the above atmosphere.
The As1-XPX layer was grown for 60 minutes to form a relaxed layer.

Next, in order to add nitrogen that acts as an isoelectronic trap into the epitaxial single crystal, epitaxial growth is performed for 100 minutes while introducing ammonia gas at a rate of 250 cc/min together with the above atmosphere. An N-type GaAs0.35P0.65 epitaxial single crystal layer containing the following was formed as an N-type light emitting layer. The partial pressures of the Ga component and the partial pressures of P and As at the time of forming this N-type light emitting layer are 0.0054 atm and 0.0034 atm, respectively. Next, the introduction of hydrogen sulfide gas for doping sulfur, which is an N-type dopant, was stopped, and instead, dimethylzinc, a P-type dopant, was introduced at a rate of 1 cc/min together with the above atmosphere. At the same time, the hydrogen chloride gas, phosphine gas, and arsine gas were supplied at 30 cc/min, 4
The rate was increased to 20 cc/min and 230 cc/min, and a P-type GaAs0.35P0.65 epitaxial crystal layer containing nitrogen was grown under these conditions as a P-type injection layer for 25 minutes, and then the temperature of the electric furnace was lowered and the epitaxial wafer was taken out. Ta. Partial pressure of Ga component and P at the time of forming this P-type injection layer
The partial pressures of and As are 0.0015 atm and 0, respectively.
．． 0011 atm. The results of measuring the layer thickness and carrier concentration of each layer of the epitaxial wafer thus obtained are shown in Table 1 below.

[0013]

[Table 1]

In order to manufacture a light emitting diode using this epitaxial wafer, Be containing 1% Au is deposited on the surface of the epitaxial layer, and Ge containing 12% Au is deposited on the back surface of the GaP substrate. After alloying in hydrogen gas and maintaining the temperature at 450°C for 10 minutes, a 300 μm square chip-shaped light emitting device was constructed, which was then mounted on a lead frame and sealed with resin. A light emitting diode with a diameter of 5 mm was constructed. When we measured the luminance of the light, we found that when the operating current was 20 mA, the light emission wavelength was 63.
A high luminance of 0 nm and a luminance of 480 mcd was obtained. This is similar to the conventional N-type GaAs1 obtained by the gas phase method.
-The brightness is approximately 2.2 times higher than that of an orange light-emitting diode with a wavelength of 630nm created by thermally diffusing zinc onto the epitaxial surface of the The brightness is almost the same level.

[0015]

[Example 2] Using the same reaction system as in Example 1, hydrogen gas
l/min, hydrogen chloride gas 60cc/min, nitrogen gas 100cc/min
Hydrogen sulfide gas diluted to ppm 80cc/min, 10% phosphine gas diluted with hydrogen gas 930cc/min, 10% arsine gas diluted with hydrogen gas 0cc/min6
The rate was gradually increased from 0 minutes to 210 cc/min to grow an N-type grading layer. Subsequently, the amount of 10% arsine gas introduced was kept constant at 210 cc/min, and a relaxation layer was epitaxially grown for 40 minutes to alleviate defects generated in the grading layer. Next, ammonia gas 28
N-type GaAs with nitrogen introduced for 40 minutes at 0 cc/min.
An N-type light emitting layer of 1-XPX was epitaxially grown. At this time, the partial pressure of Ga and the partial pressures of phosphorus and arsenic are equal, and both are 0.0099 atm. Subsequently, hydrogen sulfide gas was stopped, diethylzinc 0.8 cc/min was introduced, and hydrogen chloride gas 180 cc/min, 10% phosphine gas 1170 cc/min, and 10% arsine gas 630 cc/min were introduced.
Epitaxial growth of a P-type GaAs1-XPX layer containing nitrogen was performed for 15 minutes. At this time, Ga
The partial pressure of phosphorus and arsenic are equal, and both are 0.0
It is 25 atm.

[0016] As a result of manufacturing a light emitting diode under the same conditions as in Example 1 and measuring its brightness, it was found that the center emission wavelength was 625 nm and its brightness was 590 mcd, which is higher than that of the light emitting diode using the liquid phase method described above. exceeds the brightness of 520mcd,
An extremely bright light emitting diode was obtained.

[0017]

[Example 3] Using the same reaction system as in Example 1, hydrogen gas
l/min, hydrogen chloride gas 110cc/min, nitrogen gas 10
80 cc/min of hydrogen sulfide gas diluted to 0 ppm, 700 cc/min of 10% phosphine gas diluted with hydrogen gas, and 10% arsine gas diluted with hydrogen gas were sequentially increased from 0 cc/min to 385 cc/min in 60 minutes. A grading layer of the mold was grown. Subsequently, the amount of 10% arsine gas introduced was kept constant at 385 cc/min, and a relaxation layer was epitaxially grown for 40 minutes to alleviate defects generated in the grading layer. Next, ammonia gas 3
N-type GaA with nitrogen introduced for 40 minutes at 10 cc/min.
An N-type light emitting layer of s1-XPX was epitaxially grown. At this time, the partial pressures of Ga, phosphorus P, and arsenic As are equal, and both are 0.017 atm. Subsequently, hydrogen sulfide gas was stopped, diethyl zinc 0.8 cc/min was introduced, and hydrogen chloride gas 330 cc/min, 10% phosphine gas 1400 cc/min, and 10% arsine gas 770 cc/min.
P-type GaAs1-XPX with nitrogen increased to c/min
Epitaxial growth of the layer was carried out for 10 minutes. At this time, G
The partial pressure of a is 0.042 atm, and the partial pressures of phosphorus and arsenic are 0.
014 atm.

[0018] As a result of manufacturing a light emitting diode under the same conditions as in Example 1 and Example 2 and measuring its brightness, it was found that the center emission wavelength was 630 nm and its brightness was 430 mcd. A bright light emitting diode was obtained with a brightness approximately twice that in the light emitting diode.

[0019]

According to the present invention, GaAs1-XPX containing nitrogen (where 0.4≦x≦
0.9) When growing an epitaxial wafer and forming a PN junction by a vapor phase method, N-type GaAs1-XP containing nitrogen is used.
By growing the X epitaxial layer at a relatively low partial pressure and growing the nitrogen-containing P-type GaAs1-XPX epitaxial layer at a relatively high partial pressure, a layer thickness sufficient to efficiently extract light emission from inside the crystal can be achieved. A P-type layer can be grown under conditions of low diffusion.

Claims (1)

[Claims] Claim 1: G having a PN junction on a GaP single crystal substrate
In a method for manufacturing an epitaxial wafer for a light emitting diode in which aAs1-XPX (where 0.4≦x≦0.9) single crystal layer is grown by vapor phase epitaxial growth, N-type GaAs1-XPX containing nitrogen atoms is grown during epitaxial growth. The partial pressure of Ga component and the partial pressure of phosphorus and arsenic components are 0.00.
3 to 0.02 atm, P-type G containing nitrogen atoms
aAs1-XPX epitaxial growth, the partial pressure of Ga component and the partial pressure of phosphorus and arsenic components are set to 0.01 to 0.05a.
1. A method for manufacturing an epitaxial wafer for light emitting diodes, characterized in that tm.