ADSORPTION AND DIMER EXCHANGE PROCESSES IN SURFACTANT-MEDIATED EPITAXIAL-GROWTH OF GAAS INAS/

We investigate, using first-principles total energy calculations, the initial steps of adsorption and dimer-exchange mechanisms in the surfa ctant-mediated epitaxial growth of InAs over GaAs(001) surface with Te as a surfactant. We find that on the Ga-terminated GaAs(001) surface, covered by Te atoms, the dimer exchange between the layer of Te atoms and an overlayer of As atoms, based on a first neighbour exchange pro cess, is only partial, in agreement with recent experimental results. On the other hand, if the exchange process between As and Te atoms occ urs after the deposition of In and As atoms, in a second neighbour exc hange process, our results indicate a complete segregation of Te atoms , reducing the surface total energy. The Te atoms also prevent the ads orption of As, molecule on neighbour sites, avoiding the formation of As clusters. (C) 1998 Published by Elsevier Science B.V. All rights re served.