Rare-earth monosulfides are shown to offer attractive alternatives to the commonly used cesiated surfaces to reach negative electron affinity at various III-V semiconductor surfaces. This is illustrated by theoretical calculations of metallic overlayers of LaS on a semiconducting InP substrate using first-principles techniques. The combination of these materials is demonstrated to result in a very low work function (0.8 eV). The interface between the LaS overlayer/InP substrate is shown to be quite stable, and the lattice relaxation of the surface atoms and the atoms at the interface is found to be small.

• Received 20 April 2001

DOI:https://doi.org/10.1103/PhysRevB.65.033304