Characteristics and Time-Dependent Instability of Ga-Doped ZnO Thin Film Transistor Fabricated by Radio Frequency Magnetron Sputtering

We report on the fabrication and electrical characteristics of Ga-doped ZnO thin film transistors (TFTs). Low Ga-doped (0.7wt%) ZnO thin films were deposited on SiO₂/p−Si substrates by rf magnetron sputtering. The GZO TFTs show a mobility of 1.76 cm²/V⋅s, an on/off ratio of 1.0×10⁶, and a threshold voltage of 35 V. The time−dependent instability of the TFT is studied. The V_TH shifts negatively. In addition, the device shows a decrease of the on/off ratio, mainly due to the increase of the off-current. The mechanisms of instability are discussed.