In this paper, we study the ambipolar behavior of a-SiGe:H thin-film transistors fabricated at 200 °C. A sub-threshold slope and an on/off current ratio of 0.34 V/DEC and 10⁵, respectively, were measured for the n-type region, whereas values of 0.15 V/DEC and 10⁴ for were measured for the p-type region. We also obtained the characteristic energies for the deep localized states of the a-SiGe:H film, the flat-band voltages, and threshold voltages among other device parameters for the ambipolar thin-film transistors.