Stability of a-InGaZnO thin film transistor under pulsed gate bias stress

We investigated the stability of amorphous InGaZnO (a-IGZO) thin film transistor (TFT) under pulsed gate bias stress with light illumination, and compared that with DC bias stress. In the case of DC gate bias stress, a-IGZO TFT showed considerable degradation only when the negative gate voltage was applied under light illumination. For the pulsed gate bias stress, we constructed a voltage square wave with a bi-level of − 20 V and 0 V and also made variations in the time duration of − 20 V level in a cycle. Although the accumulated time duration of applying − 20 V in the pulsed gate bias stress was the same with that of DC − 20 V stress, the degradation was much reduced compared with DC bias stress. On the basis of the experimental results, we propose possible degradation mechanisms related with the role of subgap states.