Effects of change of oxygen vacancy on hysteresis voltage and stability under time-temperature dependence positive bias stress in amorphous SZTO transistors

Abstract

The study on voltage hysteresis (VHys) and instability under the time dependence positive bias stress at a fixed temperature (PBTS) in amorphous silicon zinc tin oxide (a-SZTO) thin-film transistors (TFTs) has been investigated by varying the oxygen flow rate (OFR) during the a-SZTO channel material growth via radio frequency (RF) sputtering. Current-voltage (I-V) measurement was initially taken to study the VHys, which revealed that the VHys was widened by increasing the OFR. The threshold voltage (Vth) shift in a-SZTO TFTs and the impact of OFR on electrical properties and electrical stability of a-SZTO TFTs were analyzed by the PBTS measurement. From PBTS, we observed that the threshold voltage shift difference (∆Vth) increases as the OFR increases. We conclude that a plausible reason for these results may be due to the acceptor-like trap states induced by OFR. The density of Gaussian-like states, excess or weakly bonded oxygen acting as acceptor-like states, is increased by increasing OFR during the deposition of channel material. These results are expected to be of general importance for future works of other amorphous oxide based TFTs.