Localization of electronic states at free semiconductor surfaces

We present calculations of layer densities of states (LDOS) for the unreconstructed Ge(100) surface using a tight-binding Hamiltonian. Total LDOS's, i.e., summed over the two-dimensional Brillouin zone, converge to the corresponding bulk LDOS within about four layers, in good agreement with results of self-consistent caiculations. In contrast, the localization properties of wave-vector-resolved LDOS's, which correspond to angular-resolved photoemission spectra, depend strongly on the value of the surface wave vector. In particular, at the zone edges, the LDOS's converge to the corresponding bulk LDOS within only two layers, whereas at the zone center, surface-induced structure in the LDOS persists over more than ten layers. © 1979 The American Physical Society.