Environment-dependent metastability of passivation-free indium zinc oxide thin film transistor after gate bias stress

We investigated the effects of bias stress on a passivation-free InZnO thin-film transistors (a-IZO TFTs) exposed to either the atmosphere or a vacuum. The magnitude of threshold voltage shift increased with the application duration of bias stress, to an extent that was much larger in the atmosphere than in the vacuum. The threshold voltage recovered slowly to its nearly initial value when the gate bias stress was removed. The electrical metastability was attributed to the interaction between the exposed a-IZO backchannel and oxygen/moisture from the atmosphere, and a dynamic equilibrium was finally achieved, regardless of the polarity of stress voltage.