Chemical and electronic structure of compound semiconductor–metal interfaces

Chemical reaction and diffusion at semiconductor–metal interfaces can be analyzed on an atomic scale using the extreme surface sensitivity of soft x‐ray photoemission spectroscopy (SXPS). For metal layers on III–V compound semiconductor surfaces cleaved in UHV, SXPS reveals that interface widths of semiconductor anions bonded to metal vary from hyperabrupt to tens of Å, scaling with interface chemical reactivity. For II–VI compounds, mixed anion–metal–cation bonding and reactive diffusion are more evident, leading to even more extended interface widths at room temperature. Absolute semiconductor dissociation and constituent diffusion into Au overlayers (weak chemical bonding) scales linearly with bulk compound stability. The extent and stoichiometry of interdiffusion can be controlled by reactive metal interlayers only a few Å thick. The altered chemical structures lead to significant changes in interface electronic structure and Schottky barrier height. The strength and nature of chemical bonding controls formation of both reacted layers with new dielectric properties and interdiffused layers with new electrically active sites at the extended interface.