A Two-Step Electrical Degradation Behavior in α-InGaZnO Thin-Film Transistor

In this study, we explored the threshold voltage instability behavior in amorphous indium-gallium-zinc oxide (alpha-IGZO) thin-film transistor (TFT). A tow-step electrical degradation behavior of alpha-IGZO TFT was found under gate-bias stress. A usual small positive shift followed by a special negative shift of threshold voltage is characterized in the alpha-IGZO TFT. We suggest that the positive shift of the threshold voltage is because of charge trapping in the gate dielectric and/or at the channel/dielectric interface, while the negative shift of threshold voltage may be attributed to electric field induced extra electron carriers from H2O molecules in the back channel protective layer.