Characterization of High-Current Stress-Induced Instability in Amorphous InGaZnO Thin-Film Transistors by Low-Frequency Noise Measurements

The instability of amorphous InGaZnO thin-film transistors is investigated under high drain current stress by applying bias voltages to both gate and drain electrodes. The instability involves positive threshold voltage shift, reduction of the ON-state current and recovery of the transfer characteristic toward the prestressed state when the stressed device is unbiased in dark at room temperature for an extended period. This instability behavior is investigated by low-frequency noise measurements before and after stress in the forward and reverse configurations. The overall results are consistent with the instability mechanism involving electron trapping in the existing donor-like gate oxide trap states near the source side.