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

Abstract

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.