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-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 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 Vth increases due to charge detrapping of the previously trapped charges. As L increases, the negative shift of Vth increases due to the decreased charge detrapping time and high electric field induced by a small subgap density of states.