This paper presents the study of an interface preparation procedure in the source/drain regions of the active layer, prior to deposit the n+ a-Ge:H contact layer in the fabrication process of low-temperature a-SiGe:H thin-film transistors. The devices were fabricated on corning 1737 substrates at 200 °C. The improvement in metal–semiconductor interface by the interface preparation procedure was demonstrated. This interface improvement translates in higher mobility and better values of off-current, on/off-current ratio, subthreshold slope and threshold voltage.