Influence of Illumination on the Negative-Bias Stability of Transparent Hafnium–Indium–Zinc Oxide Thin-Film Transistors

The stability of transparent hafnium-indium-zinc oxide (HIZO) thin-film transistors (TFTs) was investigated under negative-bias stress conditions. TFTs that incorporate transparent electrode materials such as indium-tin oxide or indium-zinc oxide were studied, and the bias stress experiments showed that transparent TFTs undergo severe degradation (negative shift in threshold voltage VT) with simultaneous exposure to white light, in comparison with the results obtained in dark. The time evolution of VT indicates that the deterioration under illumination occurs mainly by the trapping of photogenerated carriers near the HIZO/dielectric interface.