Patent ID: 8574364

Claim:
A GaN-crystal free-standing substrate comprising a first crystal region having a carbon concentration of 5×10 16 atoms/cm 3 or less, a silicon concentration of 5×10 17 atoms/cm 3 or more and 2×10 18 atoms/cm 3 or less, and an oxygen concentration of 1×10 17 atoms/cm 3 or less; and a second crystal region having a carbon concentration of 3×10 16 atoms/cm 3 or less, a silicon concentration of 5×10 17 atoms/cm 3 or less, and an oxygen concentration of 5×10 17 atoms/cm 3 or more and 5×10 18 atoms/cm 3 or less, wherein the first crystal region and the second crystal region appear in the same physical plane.