O-vacancy as the origin of negative bias illumination stress instability in amorphous In-Ga-Zn-O thin film transistors

We find that O-vacancy (Vo) acts as a hole trap and play a role in negative bias illumination stress instability in amorphous In-Ga-Zn-O thin film transistors. Photo-excited holes drifted toward the channel/dielectric interface due to small potential barriers and can be captured by Vo in the dielectrics. While Vo(+2) defects are very stable at room temperature, their original deep states are recovered via electron capture upon annealing. We also find that Vo(+2) can diffuse in amorphous phase, including hole accumulation near the interface under negative gate bias.