Performance and stability of Al-doped HfGaO thin-film transistors deposited by vapor cooling condensation system

Abstract

In this work, to study the features of Al atomic ratio in Al2O3-doped HfGaO (referred as AlHfGaO) channel layers of thin-film transistors, the HfGaO and various AlHfGaO films were deposited at approximately 80 K using a vapor cooling condensation system. The oxygen vacancy defects resided in AlHfGaO films and the defect density in the resulting thin-film transistors decreased with an increase of the Al atomic ratio. As defects reduced, threshold voltage and on/off current ratio increased, while threshold voltage offset and subthreshold swing decreased. In terms of the threshold voltage offset, measured by positive gate bias stress and negative gate bias stress methods, as the stability parameter of thin-film transistors, the stability was improved by using a higher Al atomic ratio in the AlHfGaO channel layers due to the suppression of the charge trapping effect.