Transition of dominant instability mechanism depending on negative gate bias under illumination in amorphous In-Ga-Zn-O thin film transistor

The gate bias dependence on the negative bias instability under illumination was examined. As the gate bias got more negative, dominant mechanism was changed from simple charge trapping to that accompanied by generation of subgap states. Degree of threshold voltage shift was not monotonously dependent on the magnitude of negative gate bias. It is strongly related with the corresponding instability modes for different gate bias regimes. The transition of instability mechanism depends on how much the gate bias stabilizes ionized oxygen vacancy states. (c) 2011 American Institute of Physics. [doi:10.1063/1.3540500]