Bias-stress stability of top-gate coplanar a-ITGZO TFTs with HfO2 and HfAlO gate dielectrics

Abstract

In this study, we investigated the electrical characteristics of amorphous indium-tin-gallium-zinc-oxide thinfilm transistors (TFTs) (a-ITGZO TFTs) with HfO2 and HfAlO gate dielectrics. The mobilities of the a-ITGZO TFTs with HfO2 and HfAlO were 32.3 and 26.4 cm(2)/V &.s, respectively. The TFT with HfO2 showed a subthreshold swing (SS) of 206 mV/dec and a hysteresis window of 0.60 V, and the TFT with HfAlO showed an SS of 160 mV/dec and a hysteresis window of 0.12 V. The hysteresis windows were related to the interface trap density. The TFT with HfO2 was more vulnerable to positive bias stress; in contrast, the TFT with HfAlO operated stably even after it experienced positive and negative bias stresses for 3000 s.