Effects of Ambient/Carrier Gas on Amorphous InGaZnO-Based Thin-Film Transistors Using Ultrasonic Spray Pyrolysis Deposition

This study investigates how ambient/carrier gases affect the material characteristics of amorphous indium–gallium–zinc oxide (a-InGaZnO) thin films deposited using the ultrasonic spray pyrolysis deposition (USPD) method. Nitrogen and air are used as the ambient/carrier gases in this study. The crystallinity, oxygen deficiency, energy bandgap, and trap level in the a-InGaZnO thin films are analyzed. The performance of the thin-film transistors (TFTs) based on a-InGaZnO with different ambient/carrier gases is investigated as well. It is found that oxygen deficiency is suppressed when air is used as the ambient/carrier gas. When nitrogen is used as the ambient/carrier gas to deposit a-InGaZnO thin film, the TFT shows higher field-effect mobility and saturation mobility. However, when the a-InGaZnO thin film is deposited with air as the ambient/carrier gas, the subthreshold swing, ON-/ OFF-current ratio, interface trap density, and stability of the TFT are improved. This study demonstrates how ambient/carrier gases in the USPD system affect the performance of a-InGaZnO TFT.