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 repre sentative of these surfaces. In modeling GaN surfaces and GaN/SiC inte rfaces we have used the following clusters: (i) surface (100), Ga2NH4, Ga2N2H4, Ga2SiH4, Ga2CH4, GaSi2H6, Ga2H6, NSi2H6; (ii) surface (110), GaNH4 and Ga2N2H6, and (iii) surface (111), GaN3H9 and Ga3NH9. The re sults are compared with experiments and previous theoretical calculati ons. We conclude that the surface relaxations are mainly determined by local rehybridization or valence effects and are basically independen t of energy band features. (C) 1997 Elsevier Science S.A.