Enhanced Performance of ZnO Thin-Film Transistors with ZnO Dual-Active-Layer

Thin-film transistors using reactive sputtering ZnO with metallic zinc target are fabricated in this work. The maximum processing temperature used is 150 degrees C.The performance of TFTs with high/low-resistivity ZnO dual-active-layer grown at different O-2/Ar flow rate ratio (0.75 and 0.8) is investigated. The experiment results show that the surface properties of channel layer play an important role in controlling of the field effect mobility and threshold voltage. The best performance device is obtained with ZnO dual-active-layer, which has the best surface morphology and moderate grain size. The resulting TFT has a field effect mobility of 8.1 cm(2)/V.s, a threshold voltage of 5.6V, an on/off current ratio of more than 10(7) and a subthreshold swing of 0.92 V/dec.