Quantitative analysis of interface trap recovery caused by repetitive bending stress in flexible oxide thin-film transistors

We quantitatively characterized the thermal recovery process of flexible top-gate amorphous InGaZnO thin-film transistors stressed by repetitive mechanical bending. The interface trap density increases due to repetitive bending stress concentrated at the interface between the InGaZnO and Al2O3 layers near the source and drain electrodes. After 40 000 bending cycles, an increase in series resistance and subthreshold slope degradation is observed. Then, the restoration of the subthreshold slope is monitored over several hours at elevated temperatures. The threshold voltage remained nearly constant during this process. We propose a stretched exponential approach to the time-dependent subthreshold slope restoration to quantify the recovery of interface trap density at various temperatures. We present the method to extract the activation energy required for thermal relaxation of the interface trap sites generated by repetitive bending stress.