Schottky-barrier formation at low metal coverages: A consistent molecular-orbital calculation for K on GaAs(110)

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Abstract
A molecular-orbital method is used to analyze the early stages of the K-GaAs(110) interface formation. From our analysis we conclude that the first K atoms deposited on the semiconductor are bonded to Ga, while for a full monolayer coverage a disordered metal geometry may appear. Our results also show a slight evolution in the Fermi level; that for a small K coverage is around 0.9 eV, while that for a monolayer is 0.65 eV. We find that in all the cases the Fermi level is pinned by the adatom-induced density of states in the semiconductor energy gap: The Fermi-level shift as a function of the metal coverage is explained as due to the modification of the semiconductor charge-neutrality level.