X-ray photoemission spectrum of the III–VI layer compound GaTe in the region of the valence bands

The X-ray photoemission spectra of the monoclinic III–VI layer semiconducting compound GaTe have been measured, obtaining well resolved features never observed before with the same technique. An overall similarity is found to the XPS spectra of GaS, GaSe and InSe, the III–VI compounds with hexagonal lattices. To interpret the XPS data, we have computed the electronic band structure of GaTe, introducing for it a model hexagonal lattice. The Overlap Reduced Semiempirical Tight Binding method has been used for the computation, and we have fitted the direct gap obtained as the limit for x = 0 of the experimental values for the mixed compounds GaSexTe1−x. The computed density of states allows us to interpret the main features of the XPS of GaTe up to the binding energy of about 4 eV, while for higher energies effects probably related to the monoclinic structure are revealed.