STRUCTURE AND ENERGETICS OF AS DIMERS ON GAAS(CHALCOGEN)(001) SURFACES AND GAAS TE/INAS INTERFACE/

We have performed first principles calculations for the adsorption of As-2 molecules over GaAs:Te, GaAs:Se and GaAs:S(001) surfaces. We inve stigate the dimer exchange process between the adsorbed As-2 dimer and the sublayer chalcogen atoms. The adsorption on Te terminated surface and the subsequent exchange process, confirm the surfactant action of Te atoms. For Se and S covered surfaces, the adsorption of As-2 molec ule is an exothermic process, but the subsequent Se(S) <-> As exchange process is not energetically favourable. The GaAs/Te/InAs interface w ith half a monolayer of Te is also considered. For the interface we fi nd a valence-band offset of 0.18 eV. (C) 1998 Elsevier Science B.V.