Low‐Voltage MgZnO Thin Film Transistors with an Amorphous Al 2 O 3 Gate Insulator Grown by Pulsed Laser Deposition

In this paper, MgZnO thin‐film transistors (TFTs) is fabricated using amorphous Al 2 O 3 as the gate dielectric layer by pulsed laser deposition (PLD). The electrical performance of MgZnO‐TFTs based on a channel layer grown at 300 °C shows saturation mobilities (µ sat ) of ≈6.70 cm 2  V −1  s −1 , threshold voltages ( V T ) of ≈0.70 V, a subthreshold swing ( SS ) of ≈0.138 V dec −1 , and an I on / I off ratio of 10 6 . The threshold voltage and the subthreshold swing of the devices is greatly reduced compared to some previous reports for MgZnO‐TFTs. The quality of the Al 2 O 3 gate insulator deposited under different oxygen pressures is investigated. The results shows that the crystallinity of the Al 2 O 3 thin film decreases with increasing oxygen pressures from 0.01 to 5 Pa until an amorphous Al 2 O 3 thin film is obtained at 5 Pa. The MgZnO active layer grown on the amorphous Al 2 O 3 thin film has the best crystal quality with the smallest number of defects. Our research demonstrates that an amorphous Al 2 O 3 thin film is a promising gate dielectric candidate for high‐performance oxide TFTs.