Electronic structure of Ge overlayers on (100) GaAs

We report calculations of the electronic structure of one, two, and three Ge layers on semiinfinite Ga-terminated (100) GaAs using empirical tight-binding Hamiltonians for the bulk-material description. The theoretical approach used to treat these overlayer systems is an extension of our method for the treatment of heterojunction interfaces, which is based on the Koster–Slater idea for treating localized perturbations. Our results show that the wavevector-integrated layer densities of states for the overlayer systems are not strongly influenced by surface–interface interactions. The wavevector-resolved layer densities of states, however, show pronounced features which are induced by surface–interface interactions. In particular, a new peak at about 9 eV below the valence-band top is found to dominate the layer density of states at the zone center (i.e. at the Γ point) and should be detectable by angle-resolved photoemission measurements.