Dual Active Layer Mg-Doped InZnO Thin-Film Transistors with Ultra-Low Indium Doping

Dual active layer (DAL) Mg-doped InZnO thin film transistors (TFTs) are fabricated with ultralow usage of the rare metal In. Optimized DAL MIZO TFTs are obtained by adjusting In-doping, Mg content, and the thickness of two active layers. Compared with conventional single active layer TFTs, the DAL MIZO TFTs showed improved performance in terms of carrier mobility, threshold voltage (V th ), ON-state current (I ON ), and leakage current (I OFF ). The front channel near the gate oxide has a lower Mg-doping and a higher In-doping compared with that of back channel, providing a high carrier concentration (n e ) to increase I ON . The back channel has a higher Mg-doping and a lower In-doping, providing a low n e to suppress I OFF . Furthermore, the heterojunction potential barrier formed between the two channel layers also helps to suppress the I OFF of the DAL TFTs.