Sputtered ZnO thin-film transistors with carrier mobility over 50 2/Vs

Polycrystalline zinc oxide (ZnO) thin-film transistors with a Ta 2O5 high-k gate dielectric layer are fabricated by radio-frequency magnetron sputtering at room temperature. Under the optimal deposition conditions, the devices show saturation mobility values over 50 cm2/Vs, an ON/OFF ratio of > 105, and a subthreshold voltage swing of 0.29 V/decade at a low operating voltage of 4 V. This is, to the best of our knowledge, one of the highest field-effect mobility values achieved in ZnO-based thin-film transistors by room-temperature sputtering. The stability of the devices is also examined and the sensitive dependence of the carrier mobility on the deposition conditions is discussed. © 1963-2012 IEEE.