Patent ID: 7982241

Claim:
An epitaxial substrate, comprising: a base constituted of α-SiC single crystal; a buffer layer formed by epitaxially growing on said base, and formed of a group III nitride expressed in a composition formula In x1 Al y1 Ga z1 N (0≦x1≦1, 0<y1≦1, 0≦z1≦1, x1+y1+z1=1), wherein an upper part of said buffer layer including a surface part of said epitaxial substrate is formed of columnar polycrystalline including a grain boundary existing on said base in a direction substantially perpendicular to the substrate surface and being oriented at a c axis, a lower part of said buffer layer which is near an interface with said base has more grain boundaries than said upper part of said buffer layer, transition of shape of crystalline grain between said lower part and said upper part of said buffer layer is local and gradational, and a full width at half maximum of an X-ray rocking curve (0002) ω scan of said upper part of said buffer layer is not less than 300 seconds and not more than 3000 seconds.