Sputter‐deposited Ga–Sn–Zn–O thin films for transparent thin film transistors

Ga–Sn–Zn–O (GTZO) thin films were prepared on glass substrates at 100 °C by co‐sputtering of Ga‐doped ZnO and SnO2 targets. Characteristic properties of the films were investigated with varying oxygen gas content in the sputtering ambient. Whereas amorphous GTZO films were prepared with pure Ar sputtering, polycrystalline films were obtained with the addition of oxygen gas. With a proper mixing ratio of sputtering gases, O2/(Ar + O2) ∼2%, we could obtain GTZO films with good performances as an active channel material in thin film transistor (TFT); i.e, field effect mobility of 12.2 cm2 V−1 s−1, on/off current ratio of 109, and subthreshold voltage swing of 0.46 V decade−1.