Atomic structure of the GaN(100,110,111) surfaces

We have studied the relaxation of the (100), (110) and (111) surfaces of GaN by applying ‘ab initio’ quantum methods to small clusters representative of these surfaces. In modeling GaN surfaces and GaN/SiC interfaces we have used the following clusters: (i) surface (100), Ga2NH4, Ga2N2H4, Ga2SiH4, Ga2CH4, N2SiH4, N2CH4, GaSi2H6, GaC2H6, NSi2H6, and NC2H6; (ii) surface (110), GaNH4 and Ga2N2H6; and (iii) surface (111), GaN3H9 and Ga3NH9. The results are compared with experiments and previous theoretical calculations. We conclude that the surface relaxations are mainly determined by local rehybridization or valence effects and are basically independent of energy band features.