EPITAXIAL SUBSTRATE FOR FORMATION OF SEMICONDUCTOR ELEMENT FOR HIGH FREQUENCY, AND MANUFACTURING METHOD OF EPITAXIAL SUBSTRATE FOR FORMATION OF SEMICONDUCTOR ELEMENT FOR HIGH FREQUENCY

摘要

PROBLEM TO BE SOLVED: To provide an epitaxial substrate capable of implementing a semiconductor element for high frequency operation which has a cost merit and is superior in characteristics. SOLUTION: With respect to the epitaxial substrate, a foundation layer made of a first group III nitride having an insulating property is epitaxially formed on a base material made of conductive SiC or Si by an MOCVD method so that a substantially aperiodic concave-convex structure is provided on a surface. A channel layer made of GaN is epitaxially formed on the foundation layer, and a barrier layer made of AlxGa1-xN (0