Preparation of High-Performance IATO Films and Thin-Film Transistors with Investigation on Oxygen Partial Pressure Effects and Application of ALD Al₂O₃ Gate Insulator

Amorphous In–Al–Sn–O (IATO) is a very promising channel material for thin film transistors (TFTs). In this study, we first investigated the properties of IATO films and TFTs under various oxygen partial pressures (P(O2)) of RF magnetron sputtering. The IATO films were amorphous with smooth surfaces, high average absolute visible transmittances exceeding 92.0%, large optical band gaps of 4.11–4.36 eV, and a wide Hall mobility range of 8.23–84.3 cm2 V–1s–1. As P(O2) increased from 0 to 4%, the performance of the IATO TFTs gradually degraded. Under P(O2) of 0%, the IATO TFTs exhibited high field-effect and saturation mobilities exceeding 10 cm2 V–1 s–1, high on/off current ratios of 3.42 ± 0.13 × 109, and the best positive and negative bias stress stability. Upon replacing the SiO2 gate insulator with atomic layer deposited Al2O3, further enhanced overall performance of IATO TFTs was achieved, including high saturation mobilities of 13.1 ± 0.13 cm2 V–1 s–1, low threshold voltages of 1.17 ± 0.10 V, low subthreshold swings of 106 ± 6.2 mV dec–1, and low hysteresis values of 0.09 ± 0.01 V. They also demonstrated excellent bias stability, with the maximum threshold voltage shifts under 3000 s of negative bias (−1 V) and positive bias (5 V) stresses being only −0.32 and +0.61 V, respectively.