Interface morphology of Al, Ge, and In overlayers on GaAs(100) by polar-angle-resolved photoemission

We have studied the formation of Al, Ge, and In overlayers on GaAs(100) surfaces by comparing angle-resolved photoemission spectra at grazing- and normal-emission angles as the interfaces were built up by successive ultrahigh-vacuum evaporations. An analysis of the changes in core-level line shapes and intensities yielded detailed information about the morphology of the developing interfaces. Different physical processes, such as out-diffusion of substrate atoms, in-diffusion of the evaporated overlayer, and island formation, could be distinguished. Effects of the substrate temperature upon interface formation processes were also studied with this technique.