Patent ID: 8546166

Claim:
A III-nitride crystal substrate manufacturing method, comprising: a step of preparing a starting undersubstrate including a III nitride crystal layer having a major face, with the major face having a predetermined angle of inclination of from 0.5° to 10° with respect to a {0001} plane of the III nitride crystal layer; a step of forming on the major face of the starting undersubstrate a plurality of micro-steps consisting of a plurality of terraced faces paralleling the {0001} plane, and of a plurality of stepped planes having a predetermined angle with respect to the {0001} plane; a step of initially growing III nitride crystal to a predetermined thickness by a liquid-phase technique onto the major face of the starting undersubstrate; a step of additionally growing III nitride crystal onto the liquid-phase grown III-nitride crystal; and a step of slicing the additionally grown III-nitride crystal through a plane paralleling the {0001} plane to produce a III-nitride crystal substrate; wherein said inclination of, and the form of said micro-steps on, the starting undersubstrate major face are predetermined such that in a major-face principal region of the III-nitride crystal substrate excluding the peripheral margin from the outer periphery of the major face to a 5 mm separation from the outer periphery, the substrate has a total density of screw dislocations, edge dislocations, and mixed screw-and-edge dislocations of between 1×10 4 cm −2 and 5×10 5 cm −2 inclusive, and has a ratio of screw-dislocation density to said total dislocation density of not less than 0.5.