GaN-crystal free-standing substrate and method for producing the same

A method for producing a GaN-crystal free-standing substrate, comprising

• a step of growing a GaN crystal by HVPE, the GaN crystal having a crystal growth plane comprising, as a crystal growth plane other than a plane on a side surface of the crystal,a(0001) plane and at least one plane of a {10-11} plane and a {11-22} plane;
• and
• a step of forming a GaN-crystal free-standing substrate by processing the GaN crystal,
• wherein, in the GaN-crystal free-standing substrate, a first crystal region grown with the (0001) plane serving as the crystal growth plane has a carbon concentration of 5×1016 atoms/cm3 or less, a silicon concentration of 5×1017 atoms/cm3 or more and 2×1018 atoms/cm3 or less, and an oxygen concentration of 1×1017 atoms/cm3 or less;
• and a second crystal region grown with the at least one plane of the {10-11} plane and the {11-22} plane serving as the crystal growth plane has a carbon concentration of 3×1016 atoms/cm3 or less, a silicon concentration of 5×1017 atoms/cm3 or less, and an oxygen concentration of 5×1017 atoms/cm3 or more and 5×1018 atoms/cm3 or less, and the first crystal region and the second crystal region appear in the same physical plane.