A crystal has a diameter of 1 cm or more and shows a strongest peak in cathode luminescent spectrum at a wavelength of 360 nm in correspondence to a band edge.

A crystal growth apparatus comprises a reaction vessel holding a melt mixture containing an alkali metal and a group III metal, a gas supplying apparatus supplying a nitrogen source gas to a vessel space exposed to the melt mixture inside the reaction vessel, a heating unit heating the melt mixture to a crystal growth temperature, and a support unit supporting a seed crystal of a group III nitride crystal inside the melt mixture.

A crystal growth apparatus comprises a reaction vessel holding a melt mixture containing an alkali metal and a group III metal, a gas supplying apparatus supplying a nitrogen source gas to a vessel space exposed to the melt mixture inside the reaction vessel, a heating unit heating the melt mixture to a crystal growth temperature, and a support unit supporting a seed crystal of a group III nitride crystal inside the melt mixture.

Provided is a self-supporting polycrystalline GaN substrate composed of GaN-based single crystal grains having a specific crystal orientation in a direction approximately normal to the substrate. The crystal orientations of individual GaN-based single crystal grains as determined from inverse pole figure mapping by EBSD analysis on the substrate surface are distributed with tilt angles from the specific crystal orientation, the average tilt angle being 1 to 10. There is also provided a light emitting device including the self-supporting substrate and a light emitting functional layer, which has at least one layer composed of semiconductor single crystal grains, the at least one layer having a single crystal structure in the direction approximately normal to the substrate. The present invention makes it possible to provide a self-supporting polycrystalline GaN substrate having a reduced defect density at the substrate surface, and to provide a light emitting device having a high luminous efficiency.

Provided is a self-supporting polycrystalline GaN substrate composed of GaN-based single crystal grains having a specific crystal orientation in a direction approximately normal to the substrate. The crystal orientations of individual GaN-based single crystal grains as determined from inverse pole figure mapping by EBSD analysis on the substrate surface are distributed with tilt angles from the specific crystal orientation, the average tilt angle being 1 to 10. There is also provided a light emitting device including the self-supporting substrate and a light emitting functional layer, which has at least one layer composed of semiconductor single crystal grains, the at least one layer having a single crystal structure in the direction approximately normal to the substrate. The present invention makes it possible to provide a self-supporting polycrystalline GaN substrate having a reduced defect density at the substrate surface, and to provide a light emitting device having a high luminous efficiency.

A CVD single crystal diamond material suitable for use in, or as, an optical device or element. It is suitable for use in a wide range of optical applications such as, for example, optical windows, laser windows, optical reflectors, optical refractors and gratings, and etalons. The CVD diamond material is produced by a CVD method in the presence of a controlled low level of nitrogen to control the development of crystal defects and thus achieve a diamond material having key characteristics for optical applications.

A CVD single crystal diamond material suitable for use in, or as, an optical device or element. It is suitable for use in a wide range of optical applications such as, for example, optical windows, laser windows, optical reflectors, optical refractors and gratings, and etalons. The CVD diamond material is produced by a CVD method in the presence of a controlled low level of nitrogen to control the development of crystal defects and thus achieve a diamond material having key characteristics for optical applications.

In one embodiment, a sheet production apparatus comprises a vessel configured to hold a melt of a material. A cooling plate is disposed proximate the melt and is configured to form a sheet of the material on the melt. A first gas jet is configured to direct a gas toward an edge of the vessel. A sheet of a material is translated horizontally on a surface of the melt and the sheet is removed from the melt. The first gas jet may be directed at the meniscus and may stabilize this meniscus or increase local pressure within the meniscus.

In one embodiment, a sheet production apparatus comprises a vessel configured to hold a melt of a material. A cooling plate is disposed proximate the melt and is configured to form a sheet of the material on the melt. A first gas jet is configured to direct a gas toward an edge of the vessel. A sheet of a material is translated horizontally on a surface of the melt and the sheet is removed from the melt. The first gas jet may be directed at the meniscus and may stabilize this meniscus or increase local pressure within the meniscus.

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.