Effects of Ultraviolet Light on the Dual-Sweep $I$ – $V$ Curve of a-InGaZnO4 Thin-Film Transistor

The instability of amorphous indium-gallium-zinc oxide (a-IGZO) thin-film transistors (TFTs) under ultraviolet (UV) light was thoroughly investigated in this paper. Unlike in a darkened state, an off-state leakage current can be found in the dual-sweep I-V transfer curve of a-IGZO TFTs under UV light illumination. Furthermore, despite the same UV light condition, the forward sweep and reverse sweep show different I-V curves, representing two different physical mechanisms. First, the subthreshold swing degradation and threshold voltage shift to the negative direction in the forward sweep are due to the total channel barrier lowering and can be confirmed by changing the light exposure region. Second, in the reverse sweep, the suggested back-channel leakage current can be controlled by dual-gate TFTs. UV light exposure of the metal-insulator-semiconductor-metal structure verifies that the off-state leakage current passes through the back channel in a reverse sweep. Finally, the physical mechanism links between forward and reverse sweeps have comprehensive interpretation in this paper.