Instability dependent upon bias and temperature stress in amorphous-indium gallium zinc oxide (a-IGZO) thin-film transistors

The effects of gate-bias stress, drain-bias stress, and temperature on the electrical parameters of amorphous-indium gallium zinc oxide (a-IGZO) thin-film transistors have been investigated. Results demonstrate that the devices suffer from threshold-voltage instabilities that are recovered at room temperature without any treatments. It is suggested that these instabilities result from the bias field and temperature-assisted charging and discharging phenomenon of preexisting traps at the near-interface and the a-IGZO channel region. The experimental results show that applying a drain-bias stress obviously impacts the instability of a-IGZO TFTs; however, the instability caused by drain bias is not caused by hot-electron generation as in conventional MOSFETs. And the degradation trend is affected by thermally activated carriers at high temperature.