Nitride semiconductor substrate and method of producing same
A nitride semiconductor substrate having a rugged surface being lapped by whetting granules to roughness between Rms5 nm and Rms200 nm, which has a function of reducing dislocations of a GaN, InGaN or AlGaN layer epitaxially grown on the lapped substrate by gathering dislocations in the epi-layer to boundaries of holes, pulling the dislocations to bottoms of the holes. Higher roughness of the nitride substrate degrades morphology of an epitaxially-grown layer thereon but reduces dislocation density to a lower level. Morphology of the epi-layer contradicts the dislocation density of the epi-layer. The nitride semiconductor substrate can reduce dislocation density and can be low cost and useful substrates.
1. A nitride semiconductor substrate being produced by a hydride vapor phase epitaxy (HVPE) method or metallorganic chloride (MOC) method and being ground by diamond, SiC or alumina fixed whetting granules at a Ga-surface till the Ga-surface roughness is between Rms 100 nm and Rms 200 nm, wherein mountains produced by grinding are quasi-uniform and have smaller heights, and holes produced by grinding are isolated, have deeper depth and are composed of {1-101}, {11-21}, {10-12}, and {1-212} facets.
2. The nitride semiconductor substrate according to claim 1 , wherein nitride semiconductor films grown epitaxially on the nitride semiconductor substrate have a surface having dislocation density between 1×10 5 cm −2 and 1.5×10 8 cm 2 .
3. The nitride semiconductor substrate according to claim 2 , wherein a process-induced transformation layer is eliminated by dry etching or wet etching after grinding the Ga-surface.