Amorphous oxide semiconductors are attracting much attention due to their high electron mobility even when processed at low temperatures. One such material is indium gallium zinc oxide (IGZO). At a temperature of 175 °C, an IGZO thin-film transistor (TFT) is demonstrated to exhibit an incremental channel mobility (μinc) of not, vert, similar17 cm2 V−1 s−1 and a turn-on voltage (Von) of not, vert, similar1 V. Given this performance, IGZO seems well-suited for TFT applications. We report on how decreasing oxygen partial pressure and increasing RF power during the sputtering deposition decreases Von towards 0 V and increases mobility. Two types of stability, constant bias testing conditions and idle shelf life, are explored and it is found that stress test stability is closely correlated to the initial value of Von, with an initial Von of 0 V resulting in improved stability.