Novel low-resistance ohmic contact to <i>n</i>-type GaAs using Cu3Ge

Abstract

We show that ε1-Cu3Ge forms a low-resistance ohmic contact to n-type GaAs. The ε1-Cu3Ge contact exhibits a planar and abrupt interface and contact resistivity of 6.5×10−7 Ω cm2 which is considerably lower than that reported for Ge/Pd and AuGeNi contacts on n-type GaAs with similar doping concentrations (∼1×1017 cm−3). The contact is electrically stable during annealing at temperatures up to 450 °C. We also show that in the Ge/Cu/n-type GaAs system, the contact remains ohmic over a wide range of Ge concentration that extends from 15 to 40 at. %. n-channel GaAs metal–semiconductor field-effect transistors using the ε1-Cu3Ge ohmic contacts demonstrate a higher transconductance compared to devices with Ge/Pd and AuGeNi contacts.