Large area seed crystal for ammonothermal crystal growth and method of making
First Claim
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1. A method for forming a free-standing ammonothermal group III metal nitride crystal, comprising:
- providing a non-gallium-nitride substrate having a coefficient of thermal expansion approximately equal to that of gallium nitride, with a value in a range of 4-8×
10−
6/K, averaged between room temperature and 700 degrees Celsius;
providing a crystalline gallium-containing nitride layer overlying the substrate;
depositing a diffusion barrier layer and an inert layer overlying at least some side surfaces of the substrate and the diffusion barrier layer, the diffusion barrier layer comprising at least one of W, TiW, Ta, Mo, and Re, and the inert layer comprising at least one of Au, Ag, Pt, Pd, Rh, Ru, Ir, Re, Ni, Cr, V, Ti, and Ta;
placing the substrate, a group III metal source, at least one mineralizer composition, and a nitrogen containing solvent within a sealable container; and
forming an ammonothermal group III metal nitride crystal on the crystalline gallium-containing nitride layer by heating the sealable container to a temperature of at least about 400 degrees Celsius.
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Abstract
Large area seed crystals for ammonothermal GaN growth are fabricated by deposition or layer transfer of a GaN layer on a CTE-matched handle substrate. The sides and back of the handle substrate are protected from the ammonothermal growth environment by a coating comprising an adhesion layer, a diffusion barrier layer, and an inert layer. A patterned mask, also comprising an adhesion layer, a diffusion barrier layer, and an inert layer, may be provided over the GaN layer to allow for reduction of the dislocation density by lateral epitaxial growth.
163 Citations
20 Claims
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1. A method for forming a free-standing ammonothermal group III metal nitride crystal, comprising:
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providing a non-gallium-nitride substrate having a coefficient of thermal expansion approximately equal to that of gallium nitride, with a value in a range of 4-8×
10−
6/K, averaged between room temperature and 700 degrees Celsius;providing a crystalline gallium-containing nitride layer overlying the substrate; depositing a diffusion barrier layer and an inert layer overlying at least some side surfaces of the substrate and the diffusion barrier layer, the diffusion barrier layer comprising at least one of W, TiW, Ta, Mo, and Re, and the inert layer comprising at least one of Au, Ag, Pt, Pd, Rh, Ru, Ir, Re, Ni, Cr, V, Ti, and Ta; placing the substrate, a group III metal source, at least one mineralizer composition, and a nitrogen containing solvent within a sealable container; and forming an ammonothermal group III metal nitride crystal on the crystalline gallium-containing nitride layer by heating the sealable container to a temperature of at least about 400 degrees Celsius. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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19. A method for forming a free-standing ammonothermal group III metal nitride crystal, comprising:
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providing a non-gallium-nitride substrate characterized by a coefficient of thermal expansion approximately equal to that of gallium nitride, with a value in a range of 5.5-6.5×
10−
6/K, averaged between room temperature and 700 degrees Celsius;providing a crystalline gallium-containing nitride layer overlying the substrate; depositing at least one patterned mask layer on the crystalline gallium-containing nitride layer to form a patterned substrate, wherein the patterned mask layer; comprises one or more of an adhesion layer, a diffusion-barrier layer, and an inert layer; comprises one or more of Au, Ag, Pt, Pd, Rh, Ru, Ir, Ni, Cr, V, Ti, or Ta; is characterized by a thickness between about 10 nanometers and about 100 micrometers; and comprises a one-dimensional or two-dimensional array of openings, wherein the openings are characterized by an opening dimension between about 1 micrometer and about 5 millimeters and a pitch dimension between about 5 micrometers and about 20 millimeters; depositing an inert layer overlying at least some side surfaces of the substrate, wherein the inert layer comprises at least one of Au, Ag, Pt, Pd, Rh, Ru, Ir, Re, Ni, Cr, V, Ti, and Ta; placing the substrate, a group III metal source, at least one mineralizer composition, and a nitrogen containing solvent within a sealable container; forming an ammonothermal group III metal nitride crystal characterized by a thickness of at least 500 micrometers by heating the sealable container to a temperature of at least about 400 degrees Celsius; and removing an ammonothermally-grown group III metal nitride crystal from the substrate and processing ammonothermally-grown group III metal nitride crystal to form a free-standing, ammonothermally-grown group III metal nitride crystal.
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20. A method for forming a free-standing ammonothermal group III metal nitride crystal, comprising:
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providing a non-gallium-nitride substrate characterized by a coefficient of thermal expansion approximately equal to that of gallium nitride, with a value in a range of 5.5-6.5×
10−
6/K, averaged between room temperature and 700 degrees Celsius, wherein the non-gallium-nitride substrate comprises a composite layer structure comprising a first large-area surface and a second large-area surface on an opposite side of the substrate from the first large-area surface;providing a crystalline gallium-containing nitride layer overlying each of the first large-area surface and the second large-area surface; depositing at least one patterned mask layer on each of the crystalline gallium-containing nitride layers to form a patterned substrate, wherein the patterned mask layer; comprises one or more of an adhesion layer, a diffusion-barrier layer, and an inert layer; comprises one or more of Au, Ag, Pt, Pd, Rh, Ru, Ir, Ni, Cr, V, Ti, or Ta; is characterized by a thickness between about 10 nanometers and about 100 micrometers; and comprises a one-dimensional or two-dimensional array of openings, wherein the openings are characterized by an opening dimension between about 1 micrometer and about 5 millimeters and a pitch dimension between about 5 micrometers and about 20 millimeters; depositing an inert layer overlying at least some side surfaces of the substrate, wherein the inert layer comprises at least one of Au, Ag, Pt, Pd, Rh, Ru, Ir, Re, Ni, Cr, V, Ti, and Ta; placing the substrate, a group III metal source, at least one mineralizer composition, and a nitrogen containing solvent within a sealable container; forming an ammonothermal group III metal nitride crystal characterized by a thickness of at least 500 micrometers by heating the sealable container to a temperature of at least about 400 degrees Celsius; and removing the ammonothermally-grown group III metal nitride crystal from the substrate and processing the ammonothermally-grown group III metal nitride crystal to form a free-standing, ammonothermally-grown group III metal nitride crystal.
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Specification