Production method for group iii nitride semiconductor and group iii nitride semiconductor

A method for producing a Group III nitride semiconductor comprising forming mesas and dents on a main surface of a substrate, and growing Group III nitride semiconductor in a c-axis direction of the Group III nitride semiconductor on the top surfaces of the mesas and the bottom surfaces of the dents, wherein

• side surfaces of the mesas and the dents are formed so as to satisfy the following conditions:
• a plane, which is most parallel to the side surfaces among low-index planes of the growing Group III nitride semiconductor, is a m-plane (1-100);
• and
• when a projected vector obtained by orthogonally projecting a normal vector of the side surface to the main surface is defined as a lateral vector, an angle formed by the lateral vector and a projected vector obtained by orthogonally projecting a normal vector of the m-plane of the growing Group III nitride semiconductor to the main surface is 0.5° or more and 6° or less.