US Patent 7867881 Method of manufacturing nitride semiconductor substrate

A method for manufacturing a nitride semiconductor substrate including the steps of: forming a nitride semiconductor layer on a sapphire substrate, and manufacturing a freestanding nitride semiconductor substrate by using the nitride semiconductor layer separated from the sapphire substrate, wherein variability of inclinations of the C-axes, being a difference between a maximum value and a minimum value of inclination of the C-axes in a radially-outward direction at each point on a front surface of the sapphire substrate is 0.3° or more and 1° or less.