In one instance, the seed crystal of this invention provides a nitrogen-polar c-plane surface of a GaN layer supported by a metallic plate. The coefficient of thermal expansion of the metallic plate matches that of GaN layer. The GaN layer is bonded to the metallic plate with bonding metal. The bonding metal not only bonds the GaN layer to the metallic plate but also covers the entire surface of the metallic plate to prevent corrosion of the metallic plate and optionally spontaneous nucleation of GaN on the metallic plate during the bulk GaN growth in supercritical ammonia. The bonding metal is compatible with the corrosive environment of ammonothermal growth.

In one instance, the seed crystal of this invention provides a nitrogen-polar c-plane surface of a GaN layer supported by a metallic plate. The coefficient of thermal expansion of the metallic plate matches that of GaN layer. The GaN layer is bonded to the metallic plate with bonding metal. The bonding metal not only bonds the GaN layer to the metallic plate but also covers the entire surface of the metallic plate to prevent corrosion of the metallic plate and optionally spontaneous nucleation of GaN on the metallic plate during the bulk GaN growth in supercritical ammonia. The bonding metal is compatible with the corrosive environment of ammonothermal growth.

In one instance, the seed crystal of this invention provides a nitrogen-polar c-plane surface of a GaN layer supported by a metallic plate. The coefficient of thermal expansion of the metallic plate matches that of GaN layer. The GaN layer is bonded to the metallic plate with bonding metal. The bonding metal not only bonds the GaN layer to the metallic plate but also covers the entire surface of the metallic plate to prevent corrosion of the metallic plate and optionally spontaneous nucleation of GaN on the metallic plate during the bulk GaN growth in supercritical ammonia. The bonding metal is compatible with the corrosive environment of ammonothermal growth.

An epitaxial structure and a method for making the same are provided. The epitaxial structure includes a substrate, an epitaxial layer and a carbon nanotube layer. The epitaxial layer is located on the substrate. The carbon nanotube layer is located in the epitaxial layer. The method includes following. A substrate having an epitaxial growth surface is provided. A carbon nanotube layer is suspended above the epitaxial growth surface. An epitaxial layer is epitaxially grown from the epitaxial growth surface to enclose the carbon nanotube layer therein. The epitaxial layer is a substantially homogenous material from the substrate.

An epitaxial structure and a method for making the same are provided. The epitaxial structure includes a substrate, an epitaxial layer and a carbon nanotube layer. The epitaxial layer is located on the substrate. The carbon nanotube layer is located in the epitaxial layer. The method includes following steps. A substrate having an epitaxial growth surface is provided. A carbon nanotube layer is suspended above the epitaxial growth surface. An epitaxial layer is epitaxially grown from the epitaxial growth surface to enclose the carbon nanotube layer therein.

A process of preparing polycrystalline group III nitride chunks comprising the steps of (a) placing a group III metal inside a source chamber; (b) flowing a halogen-containing gas over the group III metal to form a group III metal halide; (c) contacting the group III metal halide with a nitrogen-containing gas in a deposition chamber containing a foil, the foil comprising at least one of Mo, W, Ta, Pd, Pt, Ir, or Re; (d) forming a polycrystalline group III nitride layer on the foil within the deposition chamber; (e) removing the polycrystalline group III nitride layer from the foil; and (f) comminuting the polycrystalline group III nitride layer to form the polycrystalline group III nitride chunks, wherein the removing and the comminuting are performed in any order or simultaneously.

The invention provides, in one instance, a group III nitride wafer sliced from a group III nitride ingot, polished to remove the surface damage layer and tested with x-ray diffraction. The x-ray incident beam is irradiated at an angle less than 15 degree and diffraction peak intensity is evaluated. The group III nitride wafer passing this test has sufficient surface quality for device fabrication. The invention also provides, in one instance, a method of producing group III nitride wafer by slicing a group III nitride ingot, polishing at least one surface of the wafer, and testing the surface quality with x-ray diffraction having an incident beam angle less than 15 degree to the surface. The invention also provides, in an instance, a test method for testing the surface quality of group III nitride wafers using x-ray diffraction having an incident beam angle less than 15 degree to the surface.

A gettered polycrystalline group III metal nitride is formed by heating a group III metal with an added getter in a nitrogen-containing gas. Most of the residual oxygen in the gettered polycrystalline nitride is chemically bound by the getter. The gettered polycrystalline group III metal nitride is useful as a raw material for ammonothermal growth of bulk group III nitride crystals.

In a gallium nitride crystal, a nanovoid density in the crystal is less than 110.sup.5 [cm.sup.2]. A crystal growth apparatus is an apparatus for manufacturing a gallium nitride crystal, wherein a member having a B concentration of less than 1 ppm at least at a surface part is used as a member used at a part where a temperature is 500 C. or higher (high-temperature member) among members exposed to a crystal growth space. When such a crystal growth apparatus is used, a gallium nitride crystal wherein a nanovoid density in the crystal is less than 110.sup.5 [cm.sup.2] is obtained.

A process of preparing polycrystalline group III nitride chunks comprising the steps of (a) placing a group III metal inside a source chamber; (b) flowing a halogen-containing gas over the group III metal to form a group III metal halide; (c) contacting the group III metal halide with a nitrogen-containing gas in a deposition chamber containing a foil, the foil comprising at least one of Mo, W, Ta, Pd, Pt, Ir, or Re; (d) forming a polycrystalline group III nitride layer on the foil within the deposition chamber; (e) removing the polycrystalline group III nitride layer from the foil; and (f) comminuting the polycrystalline group III nitride layer to form the polycrystalline group III nitride chunks, wherein the removing and the comminuting are performed in any order or simultaneously.