Negative-Bias with Illumination Stress Induced State Creation in Amorphous InGaZnO Thin-Film Transistor

Hysteresis of InGaZnO thin-film transistor (IGZO TFT) under negative-bias with illumination stress (NBIS) was investigated using double sweeping gate voltage (V-GS) mode. We found that hysteresis of IGZO TFT was significantly enlarged by the NBIS with large negative gate voltage stress. On-current and S value in forward measurements started to show degradation under large-negative V-GS stress due to acceptor-like defect creation; on the other hand, transfer curves in reverse measurements shifted to a positive V-GS direction without S degradation. As a result of NBIS degradation, huge hysteresis can be observed. To explain the change in hysteresis under NBIS, degradation model consisting of acceptor-like bistable defects is proposed.