COMPOUND SEMICONDUCTOR SUBSTRATE, SEMICONDUCTOR DEVICE, AND PROCESS FOR PRODUCING THE SEMICONDUCTOR DEVICE

摘要

Disclosed is a compound semiconductor substrate (10). The compound semiconductor substrate (10) has a surface layer (12) on a surface thereof. The surface layer (12) is formed of a group III nitride and contains a chloride in an amount of not less than 200 × 1010 pieces/cm2 and not more than 12000 × 1010 pieces/cm2 in terms of Cl and an oxide in an amount of not less than 3.0 atomic% and not more than 15.0 atomic% in terms of O. It was newly found that the presence of a chloride in an amount of not less than 200 × 1010 pieces/cm2 and not more than 12000 × 1010 pieces/cm2 in terms of Cl and an oxide in an amount of not less than 3.0 atomic% and not more than 15.0 atomic% in terms of O in the surface layer (12) on the surface of the compound semiconductor substrate (10) can reduce the amount of Si at the interface between the compound semiconductor substrate (10) and an epitaxial layer (14) formed on the compound semiconductor substrate (10) and, consequently, the electrical resistance at the interface is reduced.