ELECTRONIC-PROPERTIES OF CESIUM ON 6H-SIC SURFACES

The adsorption of cesium on clean {0001} surfaces of n- and p-6H-SiC s amples at low temperatures was investigated by using Auger electron, x -ray photoelectron, and ultraviolet photoelectron spectroscopy as well as a Kelvin probe. At clean surfaces the Fermi level is pinned at 1.2 eV above the valence-band maximum and the ionization energy measures 5.7 and 5.8 eV on Si- and C-terminated surfaces. At 130 K, cesium grow s layer by layer. The films become metallic after the deposition of th e first Cs layer. For submonolayer coverages, Cs-induced surface donor s form at 2.95 eV above the valence-band maximum. They are due to cova lent Cs-Si bonds, The barrier height of Cs/6H-SiC Schottky contacts wa s found as 0.57+/-0.05 eV with n-type and 2.28+/-0.1 eV with p-type do ped samples. These results confirm the concept that the continuum of m etal-induced gap states determines the barrier heights of ideal metal- semiconductor contacts. (C) 1996 American Institute of Physics.