Epitaxial base substrate and epitaxial substrate

摘要

A III nitride buffer film including at least Al element and having a screw-type dislocation density of 1x10<8>/cm<2 >or less is formed on a base made from a sapphire single crystal, etc., to fabricate an epitaxial base substrate. Then, a III nitride underfilm is formed on the III nitride buffer film, to fabricate an epitaxial substrate.