Effects of Al contents on the electrical performance and low-frequency noise properties of InAlZnO thin-film transistors

This study investigates the effect of aluminum (Al) content on the electrical performance and low-frequency noise (LFN) characteristics of InAlZnO (IAZO) thin-film transistors (TFTs). Furthermore, the IAZO TFTs with Al content of 0.5 at. % exhibit a desirable device performance, which includes the field-effect mobility (µFE) of 14.1 cm2/V s, a subthreshold swing of 270 mV·dec−1, and threshold voltage (VTH) of 0.1 V. Based on the x-ray photoelectron spectroscopy band structure, photoluminescence, electron paramagnetic resonance, spectroscopic ellipsometry donor state analysis, and LFNs characterizations, the improvement in electrical properties of IAZO TFTs is attributed to the appropriate Al content (0.5 at. %) within the IAZO film. This optimal Al incorporation not only controls the carrier concentration and shallow donor state but also suppresses the oxygen-vacancy (VO) defects and passivates the trap density at the SiO2/IAZO interfaces. Moreover, the LFN measurements revealed a 1/f noise dominance of the carrier number fluctuation (ΔN) model. It can be indicated carrier trapping and release by trap states within the SiO2/IAZO interface. This work provides a precise and efficient method to evaluate the quality of the interface in IAZO TFTs.