Alkali-Metal-Induced Highest Fermi-Level Pinning Position above Semiconductor Conduction Band Minimum

Abstract

The room temperature deposition of small amounts of Cs on the InAs(110) surface induces the highest Fermi-level pinning position (∼ 0.6 eV) above the conduction band minimum ever met for any semiconductor. The Fermi-level movement is monitored by core level photoemission spectroscopy using synchrotron radiation. This striking behaviour is explained in terms of donor-type surface states induced by few Cs atoms present on InAs(110) and suggests the existence of a two-dimensional electron gas at the surface.