High-Performance Indium-Gallium-Zinc-Oxide Thin-Film Transistors with Stacked Al_2O_3/HfO_2 Dielectrics

High-performance amorphous indium-gallium-zinc-oxide thin-film transistors (a-IGZO TFTs) gated by Al_2O_3/ HfO_2 stacked dielectric films are investigated. The optimized TFTs with Al_2O_3 (2.0 nm)/HfO_2 (13 nm) stacked gate dielectrics demonstrate the best performance, including low total trap density N_\rm t, low subthreshold swing voltage, large switching ratio I_\rm ON/OFF, high mobility \mu__\scriptstyle \rm FE, and low operating voltage, equal to 1.35 \times 10^12 cm^-2, 88 mV/dec, 5.24 \times 10^8, 14.2 cm^2/V\cdots, and 2.0 V, respectively. Furthermore, a low-voltage-operated resistor-loaded inverter has been fabricated based on such an a-IGZO TFT, showing ideal full swing characteristics and high gain of \sim 27 at 3.0 V. These results indicate a-IGZO TFTs gated by optimized Al_2O_3/HfO_2 stacked dielectrics are of great interests for low-power, high performance, and large-area display and emerging electronics.