Direct determination of III-V semiconductor surface band gaps

Applying in situ combination of angle-resolved photoemission and inverse photoemission to cleaved III-V compound semiconductor (110) surfaces, we have determined the surface band gaps between the filled anion-derived dangling-bound state A₅ and the empty cation-derived state C₃ at the {Γ}{}, X{} ', X{}, and M{} points of the surface Brillouin zone. The values of the surface band gaps of the six compounds under study are found to increase in this sequence and seem to be correlated with the fundamental bulk energy gaps. The results are compared with optical surface excitations as well as electron-energy-loss experiments. The low-lying transition energies agree well with our surface band gaps at the X{} ' and X{} points.