Patent ID: 8410524

Claim:
A Group III nitride semiconductor device characterized in being furnished with: a supporting substrate composed of GaN, said supporting substrate having a screw dislocation density of not greater than 1×10 8 cm −2 and a carrier concentration of not greater than 1×10 19 cm −3 ; an undoped gallium nitride homoepitaxial layer provided on said substrate, said gallium nitride homoepitaxial layer having a thickness of from 0.5 μm to 1000 μm and a carrier concentration of not greater than 1×10 17 cm −3 ; and an Al y Ga 1−y N (0.1≦y≦0.7) epitaxial layer having a thickness of from 5 nm to 50 nm and a carrier concentration of not greater than 1×10 19 cm −3 , provided on said gallium nitride homoepitaxial layer; whereby said Al y Ga 1−y N (0.1≦y≦0.7) epitaxial layer has a full-width at half-maximum for (0002) plane XRD of 150 arcsec or less; a Schottky electrode provided on said Al y Ga 1−y N (0.1≦y≦0.7) epitaxial layer; a source electrode provided on said Al y Ga 1−y N (0.1≦y≦0.7) epitaxial layer; and a drain electrode provided on said Al y Ga 1−y N (0.1≦y≦0.7) epitaxial layer.