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 As2 molecules over GaAs:Te, GaAs:Se and GaAs:S(001) surfaces. We investigate the dimer exchange process between the adsorbed As2 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 As2 molecule is an exothermic process, but the subsequent Se(S) ↔ As exchange process is not energetically favourable. The GaAs/Te/InAs interface with half a monolayer of Te is also considered. For the interface we find a valence-band offset of 0.18 eV.