Reduction of the ZnSe/GaAs(100) valence band offset by a Te interlayer

For the heterovalent system ZnSe/GaAs(100), we have investigated the influence of a Te pretreatment of the substrate on the electronic structure of the interface by photoelectron spectroscopy. We have paid special attention to correctly determine the valence band maximum in a k-resolved fashion, including the use of photon energies which enable excitation at the Γ point. We find that the Te pretreatment leads to a decrease of the valence band discontinuity as large as 0.3 eV. From photoemission depth profiling we conclude that some Te atoms remain localized at the interface, thus causing the change of the valence band offset while others float on the ZnSe surface, probably acting as surfactants.