Schottky barrier height variation due to a Mo interfacial layer in W/GaAs systems

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Abstract
The effect of the interfacial Mo-GaAs alloy layer on the Schottky barrier characteristics of W/GaAs contacts is investigated. Variation in Schottky barrier heights is measured by fabricating W(300 nm thick)/Mo(0–10 nm)/GaAs diodes, where a Ga2 O3 layer 0.9 nm thick is previously formed on the GaAs surface. The oxide layer is intended to detect the initial stage of the interfacial reaction which could remove the oxide layer and influence electrical characteristics. The maximum barrier height and the minimum ideality factor are obtained at a Mo layer thickness of 1 nm after annealing at 450 °C. The Mo layer reduces the Ga2 O3 layer on GaAs surfaces and forms the compounds GaMo3 and Mo5 As4 with the GaAs substrates by a solid-phase reaction. The intimate contact of these compounds to the substrates is thought to be formed some distance below the original Mo/GaAs interface. The formation and control of buried Schottky barrier contacts using refractory metals are experimentally verified. This allows more reliable gate barriers for GaAs metal-semiconductor field-effect transistors.