Anomalous bias-stress-induced unstable phenomena of InZnO thin-film transistors using Ta2O5 gate dielectric

InZnO thin-film transistors using high-κ Ta2O5 gate dielectric are presented and analysed. The large capacitance coupling effect of amorphous Ta2O5 results in fabricated devices with good electrical properties. However, an anomalous negative threshold voltage (V th) shift under positive bias stress is observed. It is suggested that electron detrapping from the high-κ Ta2O5 dielectric to the gate electrode is responsible for this V th shift, which is supported both by the logarithmical dependence of the V th change on the duration of the bias stress and device simulation extracted trapped charges involved.