An ab initio study of Se-reacted GaAs(0 0 1) surfaces

Abstract

Although it is well known that Se passivates the GaAs(0 0 1) surface with respect to further growth of ZnSe, an explanation of this observation based on a microscopic picture of the surface morphology is still lacking. In this work, the surface energies of eight different configurations for the 2 × 1 reconstructed Se/GaAs surface have been determined by ab initio pseudopotential calculations. It is found that for an increasing Se chemical potential the formation of a Ga vacancy beneath the surface becomes energetically favourable, driving the surface stoichiometry towards Ga 2Se 3. The structures that match experimental observations most accurately may also account for the passivation of the Se-reacted GaAs surface.