The Role of High-κ TiHfO Gate Dielectric in Sputtered ZnO Thin-Film Transistors

Abstract

In this study, we demonstrate the role of a titanium hafnium oxide (TiHfO) gate dielectric in improving the overall electronic performance of a ZnO thin-film transistor (TFT). TixHf1-xO (x = 0.63) was fabricated by the rf co-sputtering technique. Using TiHfO as the gate dielectric, the device fabricated in this study exhibits a threshold voltage of 0.34 V, a subthreshold swing of 0.23 V/dec, a field-effect mobility of 2.1 cm2 V-1 s-1, and an ON/OFF current ratio of 105. The small subthreshold swing and low positive threshold voltage are attributed to the higher value of κ of 40 for the dielectric. This result enables device operation below 2 V, allowing its use in low-power driving circuits in display applications.