Abstract
Metals deposited on clean GaAs(110) surfaces held at low temperatures are inducing extrinsic surface states of donor type. For metals with an outer s-electron the energy levels of such surface donors are calculated in a tight-binding model. The approach used describes the adatom-substrate bonding as a diatomic, heteropolar "surface-molecule" in which the metal s-electrons are forming bonds with dangling sp3-hybrids of surface Ga-atoms. The chemical trend of the calculated energy of the bonding states as a function of the atomic term values of the metal s-electrons is in agreement with experimental data.