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 V-T) with simultaneous exposure to white light, in comparison with the results obtained in dark. The time evolution of V-T indicates that the deterioration under illumination occurs mainly by the trapping of photogenerated carriers near the HIZO/dielectric interface.