FORMATION OF METAL-SEMICONDUCTOR BARRIERS FOR GAAS-INTERFACES IN THE LOW METAL COVERAGE LIMIT

The early stages in the formation of the Schottky barrier in alkali me tal-semiconductor interfaces is analyzed theoretically for the prototy pical cases of GaAs(110) and GaAs(100) surfaces. We concentrate in des cribing the metal-insulator transition taking place as a function of t he alkali metal coverage. For each of the cases analyzed are identify two different mechanisms driving this transition: for the GaAs(110) ca se we find a typical Mott-transition which can be described by an effe ctive half-fillea Hubbard model; for the GaAs(100) case the non-local Coulomb interactions play an important role, leading for low coverages to a charge density wave insulating phase.