First-principle study of GaN polar and nonpolar surfaces

The polarity of GaN surface may have a substantial influence on its electronic structure, So the (0001) and (112̄0) surfaces and their electronic structures are studied based on density-functional theory using the local-density approximation (LDA) as well as the hybrid functional approach were studied by First-principles study. It presents the change of surface atoms position and analyses the surface electronic structure. Also the obvious relaxation appears which effects the electric field polarization direction a lot, that is the reason why our chip grown along (112̄0) surface has better property. The band gap of GaN (0001) surface is obviously narrower than that of GaN (112̄0), leading to the luminescence spectra shift red also.