A comparative study of thin-film transistors based on mist-CVD deposited InAlZnO with different Al contents

Abstract

In this study, amorphous InAlZnO thin films with varying In:Al:Zn mole ratios of 2:1:2, 4:1:4, and 8:1:8 are deposited using mist chemical vapor deposition (mist-CVD). The X-ray diffraction patterns suggest that these InAlZnO thin films are amorphous. Besides, the O 1s binding energy spectra observed by X-ray photoelectron spectroscopy, photoluminescence, and Tauc plots indicate that oxygen vacancy within the InAlZnO films decreases and bandgap energy of the InAlZnO films increases when the InAlZnO films have higher Al content. The 2:1:2 ratio yields insufficient electrical performance, while the 4:1:4 ratio obtains higher field-effect mobility of 11.42 ± 2.09 cm²V⁻¹s⁻¹, the steepest subthreshold swing of 168.57 ± 27.66 mV/dec, the largest on/off current ratio of (1.76 ± 0.3) × 10⁶, and more stable behavior under negative/positive bias illumination stress. The 8:1:8 ratio reaches the highest field-effect mobility of 27.31 ± 5.13 cm²V⁻¹s⁻¹ while scarifying the stability. This study highlights the impact of Al content on InAlZnO for thin-film transistor applications.