Atomic and electronic structure of the (311) surfaces of GaAs

Publisher Website
Google Scholar
Abstract
The polar (311) surfaces of GaAs exhibit four inequivalent bulk (1×1) terminations each of which exhibits a metallic electronic character associated with partly occupied surface states. Experimentally prepared surfaces also display a (1×1) symmetry, but the tendency for surfaces to reconstruct towards an insulating ground state suggests adatom surface structure models which yield the saturation of the surface dangling bonds. We examine two Ga–adatom models on an otherwise clean As-terminated (311) surface. Empirical total-energy minimization calculations reveal that the As-terminated surfaces exhibit two possible minimum-energy adatom structures with the top-layer (adatom) Ga in a bridge or hollow site. In the bridge-site configuration, the Ga species occupy twofold sites on top of a relaxed As-terminated surface. In the hollow-site configuration, the Ga occupy threefold sites slightly above a nearly unrelaxed surface. Both correspond to simple saturated-bond models of the surface chemical bonding but only the threefold structure is an insulator. Low-energy electron diffraction (LEED) intensities for fifteen beams have been measured at T=300 K for the experimentally inequivalent A and B surfaces. Comparison of calculated LEED intensities with the data for the B surfaces reveals the existence of two minimum-Rx regions of surface structures. Previously proposed structures associated with metallic surface states are not compatible with the experimental LEED intensities for either surface.

This publication has 0 references indexed in Scilit: