Theoretical study of the formation of a GaAs bilayer on Si(1 1 1)

We have performed first principles total energy calculations, within the density functional theory, to investigate the formation of a GaAs bilayer on the Si(1 1 1) surface. For the exchange–correlation energies we have used the generalized gradient approximation, while the electron–ion interactions were treated using ultrasoft pseudo-potentials. We have first studied the adsorption of As and Ga atoms on the Si(1 1 1) surface. A monolayer of As atoms substitutes the topmost Si layer forming an almost ideally bulk terminated configuration. On the other hand, the adsorption of 1/3 ML of Ga results in the formation of a √3 × √3 reconstruction, with Ga atoms occupying T4 sites. The deposit of 1/3 ML of Ga atoms on the As terminated Si(1 1 1) surface also results in the occupation of T4 sites. However, at full monolayer coverage, the Ga atoms occupy near top sites and form one dimensional atomic chain.