To provide an inexpensive nitride semiconductor substrate capable of epitaxially growing nitride-based semiconductor thin films such as a GaN thin film, an InGaN thin film or an AlGaN thin film low in dislocation density.
The nitride semiconductor substrate is obtained by finishing the surface of a nitride semiconductor substrate having the surface of a C-plane by lapping so that the surface roughness Rms becomes 5-200 nm. Thereby, the lapping time can be shortened markedly and the lapping cost can be reduced. The surface roughness is large and many recessed parts are included, and the crystal obliquely growing from each recessed part collects dislocations into the boundary between faces and moves the dislocations to the bottom of the recessed part from the boundary. Thereby, the dislocations are concentrated in the bottom of the recessed part, and the dislocation density of an epitaxially grown layer can be reduced. Although the morphology of the epitaxially grown layer is bad since the surface roughness of the substrate is large, the dislocation density becomes low. It becomes possible to reduce the dislocation density having a large influence on device characteristics by using the substrate, and the substrate is low in cost and useful.
MOCHIDA YASUSHI
NAKAYAMA MASAHIRO
