Patent ID: 8168516

Claim:
A method of fabricating a III-group nitride semiconductor device, the method comprising steps of: cutting an ingot of single crystal gallium nitride along predetermined planes to make one or more single crystal gallium nitride substrates, the ingot of single crystal gallium nitride being grown by vapor phase epitaxy in a direction of a predetermined axis, each predetermined plane being inclined to the predetermined axis, each substrate having a mirror polished primary surface, the primary surface having a first area and a second area, the first area being between an edge of the substrate and a line 3 millimeter away from the edge, the first area surrounding the second area, an axis perpendicular to the primary surface forming an off-angle with c-axis of the substrate, the off-angle taking a minimum value at a first position in the first area of the primary surface; growing a III-group nitride layer on the primary surface of the substrate; growing a III-group nitride active layer on the III-group nitride layer after growing the III-group nitride layer; growing a p-type III-group nitride layer on the III-group nitride active layer after growing the III-group nitride active layer; and forming a p-type electrode on the p-type III-group nitride layer and an n-type electrode on a backside surface of the substrate.