Effect of Rising Edge during Dynamic Stress With Duty Ratio in Amorphous InGaZnO Thin Film Transistors

We investigated the effects of rising edge during positive unipolar dynamic stress and bipolar dynamic stress under darkness and illumination with duty ratio D of dynamic stress from 1 to 50%. Threshold voltage shift ΔV th increased with effective time t eff as the product of stress duration and D. ΔV th was higher during bipolar stress than during positive unipolar stress and under low D than at high D. Degradation of amorphous InGaZnO thin film transistor is related to the number and amplitude of rising edges. We suggest that an additional degradation under dynamic stress is originated from high electric field in channel region at rising edge.