Polarity inversion of GaN(0001) surfaces induced by Si adsorption

We employ density-functional theory within the local-density approximation to study the structural and electronic properties of Si monolayers adsorbed at GaN(0001) surf ices. We find that when the N atoms reside in the Outermost layer of the surface, the (0001) surface converts into a (000 (1) over bar) surface, giving rise to a polarity inversion. We explain this inversion as a charge compensation effect between the N dangling bonds states at the outermost surf ace layer and the Si donor state in the subsurface layer. (c) 2005 Elsevier B.V. All rights reserved.