Refractory metal contacts to GaAs: Interface chemistry and Schottky-barrier formation

Abstract

A survey of the interface chemistry of the refractory metals W, Ta, Re, Ir, and Mo during room- temperature Schottky-barrier contact formation to GaAs by using x-ray photoemission spectroscopy (XPS) is reported. The metals were deposited onto clean n-type GaAs (100) surfaces within the XPS system by two methods: Evaporation and plasma sputtering. For each metal a distinct interfacial reaction which produced GaAs dissociation and formation of a new metal arsenide is observed. Refractory metals are in general not chemically inert in contact to GaAs and nonabrupt interfaces ∠10 Å in width are formed. XPS was also used to correlate interface chemistry with measurement of Schottky-barrier height during contact formation. XPS measured barrier heights ranged from 0.9–0.7 eV, in the order W, Ir, Mo, Ta, and Re.