Group-iii element nitride crystal producing method and group-iii element nitride crystal

a technology of group-iii element and nitride crystal, which is applied in the direction of non-metal conductors, instruments, conductors, etc., can solve the problems of reduced growth rate and easy non-uniform nucleation, and achieve efficient growth of group-iii element nitride crystal, the effect of improving crystal growth rate and suppressing non-uniform nucleation

Inactive Publication Date: 2011-01-20
RICOH KK
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Benefits of technology

[0010] In the method of producing a group-III element nitride crystal using an alkali metal as a flux, it is important to efficiently dissolve nitrogen in the flux so as to improve the growth rate. To achieve this, it is necessary to cause both the temperature of the flux and the pressure of nitrogen-containing gas (atmosphere gas) to be higher so as to increase the amount of nitrogen dissolved in flux. However, when the temperature and the pressure are high, the supersaturation degree of nitrogen in the flux increases near the gas-liquid interface between the atmosphere gas and the flux, so that nonuniform nucleation easily occurs. If nonuniform nucleation occurs at the gas-liquid interface, a polycrystal of group-III element nitride is grown as miscellaneous crystals (so-called nonuniform nucleation) based on the nuclei. Therefore, crystal growth that would otherwise occur on a seed crystal is suppressed, disadvantageously resulting in a reduction in growth rate.
[0011] Therefore, an object of the present invention is to provide a method for producing a group-III element nitride crystal, in which a crystal growth rate can be improved by suppressing the occurrence of miscellaneous crystals.
[0016] By adding a hydrocarbon having a specific boiling point to the flux during the growth of a group-III element nitride crystal using an alkali metal flux, nonuniform nucleation can be suppressed. Thereby, it is possible to efficiently grow a group-III element nitride crystal at higher temperatures and higher pressures. As a result, the crystal growth rate can be improved. Also, by coating the alkali metal with a hydrocarbon, it is possible to suppress reaction of the alkali metal with oxygen and water in an atmosphere. Further, by adding a hydrocarbon, the film thickness of a grown crystal can be uniform. As a result, the quality of the group-III element nitride crystal can be improved as well. The production method of the present invention is effective to general group-III element nitride crystals, and is particularly effective when the alkali metal is sodium and the group-III element nitride crystal is a gallium nitride crystal.

Problems solved by technology

However, when the temperature and the pressure are high, the supersaturation degree of nitrogen in the flux increases near the gas-liquid interface between the atmosphere gas and the flux, so that nonuniform nucleation easily occurs.
Therefore, crystal growth that would otherwise occur on a seed crystal is suppressed, disadvantageously resulting in a reduction in growth rate.

Method used

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  • Group-iii element nitride crystal producing method and group-iii element nitride crystal
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embodiment 1

[0068] In this embodiment, a method for producing a gallium nitride crystal will be described in which a seed crystal, sodium, gallium, and a hydrocarbon are placed in a crystal growth vessel for holding a sodium flux, and thereafter, nitrogen-containing gas is pressurized and the crystal growth vessel is heated to melt sodium and gallium, thereby generating a sodium flux.

[0069] An exemplary configuration of a production apparatus that is employed in the production method of the present invention is shown in FIG. 1(a). An exemplary closed pressure-resistant and heat-resistant vessel for use in the production method of the present invention is shown in FIG. 1(b).

[0070] The apparatus of FIG. 1(a) comprises a gas supply apparatus 1 for supplying material gas, a pressure adjuster 3 for adjusting the pressure of the material gas, a closed pressure-resistant and heat-resistant vessel 15 for conducting crystal growth, a heating apparatus 16 for heating, and an exhaust apparatus 14.

[0071...

embodiment 2

[0093] In this embodiment, a method for producing gallium nitride will be described in which a seed crystal, sodium (alkali metal) coated with a hydrocarbon, gallium (group-III element), and a hydrocarbon are placed in a crystal growth vessel for holding a sodium flux that is an alkali metal, and thereafter, a portion of the hydrocarbon is removed, followed by heating of the crystal growth vessel.

[0094] In this production method, further, the amount of the hydrocarbon in the crystal growth vessel is preferably adjusted. For example, the suppression of nucleation and the coating of the alkali metal require different amounts of the hydrocarbon. Therefore, the hydrocarbon may be added in amount required for the coating of the alkali metal in a preliminary step, and the amount of the hydrocarbon may be adjusted within an appropriate range so as to prevent dissolution of the seed crystal in an adjustment step. The adjustment of the amount of the hydrocarbon includes, for example, remova...

embodiment 3

[0102] A group-III element nitride crystal of the present invention is produced by the production method of the present invention described above.

[0103] This crystal preferably has an optical absorption coefficient of 10 cm−1 or less with respect to light having a wavelength of 400 nm or more and 620 nm or less. The optical absorption coefficient is preferably 5 cm−1 or less. Note that the lower limit of the optical absorption coefficient is a value exceeding zero.

[0104] The group-III element nitride crystal produced by the production method of the present invention may contain carbon. For example, the group-III element nitride crystal of the present invention may contain 5×1017 (cm−3) or less carbon atoms as a result of analysis by SIMS or the like.

[0105] In such a crystal, the group-III element is at least one element selected from Al, Ga and In. The group-III element nitride is preferably a compound that is represented by AlsGatIn(1-s-t)N, where 0≦s≦1, 0≦t≦1, and s+t≦1.

[0106]...

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Abstract

A method for producing a high-quality group-III element nitride crystal at a high crystal growth rate, and a group-III element nitride crystal are provided. The method includes the steps of placing a group-III element, an alkali metal, and a seed crystal of group-III element nitride in a crystal growth vessel, pressurizing and heating the crystal growth vessel in an atmosphere of nitrogen-containing gas, and causing the group-III element and nitrogen to react with each other in a melt of the group-III element, the alkali metal and the nitrogen so that a group-III element nitride crystal is grown using the seed crystal as a nucleus. A hydrocarbon having a boiling point higher than the melting point of the alkali metal is added before the pressurization and heating of the crystal growth vessel.

Description

TECHNICAL FIELD [0001] The present invention relates to a group-III element nitride crystal producing method and a group-III element nitride crystal. BACKGROUND ART [0002] Group-III element nitride compound semiconductors, such as gallium nitride (GaN) and the like, have attracted attention as materials for semiconductor devices that emit blue or ultraviolet light. Blue laser diodes (LDs) are applied to high-density optical discs and displays, and blue light emitting diodes (LEDs) are applied to displays, lights and the like. Ultraviolet LDs are expected to be applied to biotechnology and the like, and ultraviolet LEDs are expected to provide ultraviolet light for fluorescent lamps. [0003] A substrate made of a group-III element nitride compound semiconductor, such as gallium nitride (GaN) or the like, for an LD or an LED is typically produced by heteroepitaxially growing a group-III element nitride crystal on a sapphire substrate using vapor phase epitaxy. Examples of vapor phase e...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): H01B1/06C01B21/06C30B17/00H01L33/32
CPCC30B9/10C30B11/12C30B19/02H01L31/03044C30B29/406G02B1/02C30B29/403H01L33/00
Inventor YAMADA, OSAMUMINEMOTO, HISASHIHIRANAKA, KOUICHIHATAKEYAMA, TAKESHISASAKI, TAKATOMOMORI, YUSUKEKAWAMURA, FUMIOKITAOKA, YASUO
Owner RICOH KK
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