In this paper in situ x-ray photoelectron spectroscopy (XPS) is used to study the nature of the bonding at ZnSe/GaAs and CdTe/InSb interfaces grown by molecular-beam epitaxy. X-ray photoelectron spectra support the transmission electron microscopy evidence that ZnSe/GaAs MIS capacitors exhibiting low interface state densities are associated with the formation of an interfacial layer of zinc blende Ga2Se3. An interfacial layer can be deliberately introduced by reacting an As deficient GaAs surface with an incident Se flux. A comparison of the Se 3d core level features from the ZnSe epilayer surface, a Se-reacted GaAs surface, and from separately grown Ga2Se3 epilayers, clearly indicate the same Se bonding characteristic for the Se-reacted layer, and the Ga2Se3, epilayer. A parallel XPS study of CdTe/InSb interfaces leads to the conclusion that there is a general tendency for the formation of a III-VI interfacial compound when forming a II-VI-on-III-V junction.
