Patent ID: 8142566

Claim:
A method for producing a Ga-containing nitride semiconductor single crystal, comprising: providing an original substrate which is a compound semiconductor single crystal comprising zinc oxide and has a lattice constant of from 0.30 to 0.36 nm in the a-axis direction and from 0.48 to 0.58 nm in the c-axis direction; forming an initial nitride semiconductor layer on the original substrate; growing on the initial nitride semiconductor layer a Ga-containing nitride semiconductor single crystal having a composition represented by a formula, B x Al y Ga z In l-x-y-z N s P t As l-s-t , where 0≦x≦1, 0≦y<1, 0<z≦1, 0<s≦1 and 0≦t<1, the growing comprising growing a first Ga-containing nitride semiconductor single crystal layer on the initial nitride semiconductor layer at a first temperature, T 1 , and growing a second Ga-containing nitride semiconductor single crystal layer on the first Ga-containing nitride semiconductor single crystal at a second temperature; and removing the original substrate substantially in entirety, after forming the first Ga-containing nitride semiconductor single crystal layer and before forming the second Ga-containing nitride semiconductor single crystal layer, at a third temperature, T 3 , satisfying 0° C.≦|T 1 -T 3 |≦100° C., wherein the composition of the Ga-containing nitride semiconductor single crystal satisfies at least one of: the maximum reflectance measured by irradiating the Ga-containing nitride semiconductor single crystal with light at a wavelength of 450 nm is 20% or less and the difference between the maximum reflectance and the minimum reflectance is within 10%; the ratio of maximum value to minimum value of the dislocation density measured by a cathode luminescence method is 10 or less; and the lifetime measured by a time-resolved photo-luminescence method is 95 ps or more.