Channel Length-Dependent Charge Detrapping on Threshold Voltage Shift of Amorphous InGaZnO TFTs Under Dynamic Bias Stress

The demand for amorphous InGaZnO (a-IGZO) thin-film transistors (TFTs) has been increasing due to their high mobility and transparent properties. In this paper, we report on the channel length (L)-dependent charge detrapping phenomenon of a-IGZO TFTs by observing a threshold voltage $V_{\rm th}$ shift under dynamic bias stress. Dynamic gate bias stresses are applied to the devices with three types of L: 25, 50, and 100 $\mu{\rm m}$ . The positive gate bias with different stress durations is followed by the negative gate bias. Under the sequential negative gate bias stress, the reversible shift of $V_{\rm th}$ increases due to charge detrapping of the previously trapped charges. As L increases, the negative shift of $V_{\rm th}$ increases due to the decreased charge detrapping time and high electric field induced by a small subgap density of states.