Substrate for epitaxial growth, process for manufacturing GaN-based semiconductor film, GaN-based semiconductor film, process for manufacturing GaN-based semiconductor light emitting element and GaN-based semiconductor light emitting element

A substrate being formed by dry etch processing of a c-plane substrate and comprising:

• an uneven surface having a triangular prismatic or triangular truncated pyramidal convex portion which has an approximately equilateral-triangular upper surface;
• and
• a growth space being equilaterally hexagonal surrounded by six convex portions which are arranged so as to form a kagome pattern wherein a hexagonal growth surface is surrounded by six triangular convex portions, when planarly viewed, and
• wherein the growth space is a flat surface and the growth space is isolated from an adjacent growth space in the kagome pattern by two of the convex portions.

A substrate being formed by processing a c-plane substrate, comprising:

• an uneven surface having a plurality of convex portions, each having an upper surface that are arranged so that each of the convex portions has three other convex portions in directions different from each other by 120 degrees;
• and
• a plurality of growth spaces which are surrounded by six of the convex portions, and
• wherein the growth spaces are flat surfaces and the growth spaces are isolated from each other by two of the plurality of convex portions.