Ga segregation in MnSb epitaxial growth on GaAs (100) and (111) B substrates

We have found Ga segregation during the epitaxial growth of MnSb thin films on GaAs substrates by core-level photoemission spectroscopy using synchrotron radiation. MnSb films were grown on (100) and (111)B GaAs substrates by molecular beam epitaxy (MBE). While the As 3d peak intensities decrease gradually, the Ga 3d photoemission peak intensities remain unchanged even with increasing MnSb overlayer thickness. These results suggest that the Ga atoms are segregated at the surface during growth. The thickness of the segregated Ga layers is estimated to be 0.5 monolayer (ML) for MnSb on GaAs(100) and 1.0 ML for MnSb on GaAs(111)B. It is considered that the segregated Ga layer acts as a surfactant and decreases the surface energy and contributes to the layer-by-layer growth. The thickness of the surfactant layer is thought to have an influence on the surface morphology of the MnSb film.