Development of ZnO-based thin-film transistors with top gate structures

Zinc oxide (ZnO)-based thin-film transistors (TFTs) with top gate structures were produced. Radio-frequency-magnetron sputtering was used to deposit indium tin oxide for both the source and the drain electrodes and n-type undoped ZnO at high oxygen partial pressures for the active layer. Direct-current-magnetron sputtering and plasma enhanced chemical vapor deposition were used to deposit Al for the gate electrode and the SiN gate dielectric, respectively. The devices operated in the enhancement mode with a threshold voltage, mobility, on-off ratio and sub-threshold slope of 9 V, 0.05 cm2/Vs, ∼5 × 105, and 1.3 V/decade, respectively.