Annealing Treatment on Amorphous InAlZnO Films for Thin-Film Transistors

Amorphous InAlZnO (a-IAZO) films were grown by pulsed laser deposition at room temperature and annealed at various temperatures. The amorphous state of a-IAZO films is thermally stable at high temperatures up to 700 °C. The films exhibit a high visible transmittance above 95% and an appropriate resistivity on the order of 106 Ω · cm. As the annealing temperature increases, the optical bandgap and resistivity decrease in general. The microcracks form in films at an annealing temperature above 500 °C. The a-IAZO films annealed at 400 °C are suitable for channel layers of thin-film transistors (TFTs) and the devices demonstrate good performances with an on/off ratio of 108 and field-effect mobility of 2.2 cm² · V^-1 · s^-1. The observations will provide useful physical insight into film properties and also offer basic design guideline for a-IAZO TFTs.