The invention relates to a substrate for
epitaxy, especially for preparation of
nitride semiconductor layers. Invention covers a bulk
nitride mono-
crystal characterized in that it is a mono-
crystal of
gallium nitride and its cross-section in a plane perpendicular to c-axis of hexagonal lattice of
gallium nitride has a surface area greater than 100 mm2, it is more than 1.0 μm thick and its C-plane surface
dislocation density is less than 106 / cm2, while its volume is sufficient to produce at least one further-processable non-polar A-plane or M-plane plate having a surface area at least 100 mm2. More generally, the present invention covers a bulk nitride mono-
crystal which is characterized in that it is a mono-crystal of
gallium-containing nitride and its cross-section in a plane perpendicular to c-axis of hexagonal lattice of gallium-containing nitride has a surface area greater than 100 mm2, it is more 1.0 μm thick and its surface
dislocation density is less than 106 / cm2. Mono-crystals according to the present invention are suitable for epitaxial growth of nitride
semiconductor layers. Due to their good crystalline quality they are suitable for use in opto-
electronics for manufacturing opto-electronic
semiconductor devices based on nitrides, in particular for manufacturing semiconductor
laser diodes and
laser devices. The a.m bulk mono-crystals of gallium-containing nitride are crystallized on seed crystals. Various seed crystals may be used. The bulk mono-crystals of gallium-containing nitride are crystallized by a method involving
dissolution of a gallium-containing feedstock in a supercritical
solvent and
crystallization of a
gallium nitride on a surface of
seed crystal, at temperature higher and / or pressure lower than in the
dissolution process.