Passivation of GaAs(001) surfaces by chalcogen atoms (S, Se and Te)

Abstract

In order to elucidate the passivating effects of the chalcogenide solution treatment on GaAs surfaces, we have performed first-principles Pseudopotential calculations of the GaAs(001) surfaces adsorbed with a monolayer of chalcogen atoms. It is shown that chalcogen atoms adsorb in the bridge site on both the Ga-terminated and the As-terminated GaAs surfaces and form covalent bonds with Ga or As atoms. The chalcogen-Ga bond is found to be stronger than the chalcogen-As bond. We have shown that the chalcogen-Ga bond remarkably reduces the surface state density in the GaAs mid-gap region, while the chalcogen-As bond does not. It is suggested that the chalcogen-Ga bonds are dominant on the chalcogen-treated GaAs surface and are responsible for the passivation of the surface. In addition, we infer that Se atoms can passivate GaAs(001) surfaces as effectively as S atoms, but that the passivating effect of Te atoms is weak in comparison with S and Se atoms.