Solution-Processed Low-Operating-Voltage Thin-Film Transistors With Bottom-Gate Top-Contact Structure

It was demonstrated that low-operating-voltage bottom-gate top-contact (BGTC) structure thin-film transistors (TFTs) were fabricated using solution-processed amorphous zinc indium tin oxide (ZITO) and hafnium aluminum oxide (HAO) films. Due to the excellent chemical stability of ZITO film and high etching selectivity between ZITO and indium tin oxide (or between ZITO and Mo), the manufacture of BGTC structure requires only traditional lithography and wet etching. The usage of high-k HAO films lowered the operating voltage (below 2 V) of the TFT devices. TFT devices based on ZITO and HAO films annealing at 500 °C showed a saturated field-effect mobility of 13.5 cm²V^-1s^-1, a small subthreshold swing of 87 mV/decade, a large ON-to-OFF current ratio of 7.2 × 10⁶, and a threshold voltage of -0.6 V. The hysteresis (0.14 V) of TFT devices confirmed further that the ZITO and HAO films could be the promising candidates for TFT devices.