Metal-Semiconductor Interfaces and Schottky Barriers

Abstract

Over the past several years, experimental techniques from surface science, materials science, and solid state physics have brought significant progress in understanding the microscopic properties and behavior of metal/semiconductor interfaces. The outstand ing conclusion from this research is that these interfaces are chemically reactive and that this reactivity plays the dominant role in determining both microscopic properties of the interface (such as composition, atomic structure, and electronic structure) and macroscopic characteristics of the contact (such as electrical properties, lattice phase of the reaction product, and epitaxy). The interfacial reaction chemistry can be rather diverse, involving interdiffusion of metal and semiconductor, the formation of compound phases at the interface, as well as partial reaction and mixed phases. The case of transition metal/Si interfaces is discussed in particular detail, because the elemental character of the semiconductor and the formation of well-defined silicide compounds has made the interpretation of results more definitive. Though necessarily more complex, metal/III–V semiconductor interfaces display corresponding chemical behavior. Attempts to understand the microscopic mechanisms which control the Schottky barrier electrical properties of metal/semiconductor interfaces have also begun to focus on the relation between interfacial chemistry and barrier height, although a clear explanation is not yet available, either for elemental or III–V semiconductors.