Potassium reaction on sulfur-passivated GaAs(100)

Abstract

It has been confirmed by high-resolution x-ray photoelectron spectroscopy that the Fermi level of K-contacted sulfur-passivated GaAs(100) is not located at the Fermi level of the ideal Schottky contact and is pinned near the midgap, even though the initial S passivation removes the high density gap states. With K deposition the Fermi level moves to 0.5 eV above the valence band maximum for both n- and p-type surfaces. The interfacial chemical reaction shows the top As element preferentially reacts with deposited K, and the interface still has dominant Ga–S bondings. These results imply that although the reactive alkali metal such as K does not break Ga–S bondings, it induces the metallic state which pins the Fermi level at 0.5 eV above the valence band maximum.