Structure and transport properties of amorphous Ge_1-xC_x:H thin films obtained by activated reactive evaporation

Abstract

Hydrpgenated amorphous germanium-carbon (a-Ge_1-xC_x:H) thin films have been prepared by an Activated Reactive Evaporation (ARE) technique. Germanium was evaporated from a resistively heated tungsten basket through an acetylene plasma. The films thus obtained were characterized for the compositional, structural, electrical and optical properties. The effects of substrate temperature, role of hydrogen and variation of optical energy gap with carbon content were also investigated. Typically, films deposited at 200 °C showed a sharp absorption edge corresponding to an optical gap of about 1.3 eV and thermally activated electrical conduction over a wide range of temperatures.