Function of a Dual-Active-Layer Amorphous Indium–Gallium–Zinc Oxide Thin-Film Transistor with Ultraviolet-Induced Effects

This study presents an ultraviolet (UV) photodetector based on a dual-active-layer amorphous indium–gallium–zinc oxide (a-IGZO) thin-film transistor (TFT), where a Zn-rich IGZO layer is designed as a charge trapping center due to its oxygen vacancies and easy-to-generate interface defects. When a drain bias of 10 V is given, the electron injection occurs closer to the drain end, which causes the active layer to exhibit a significant resistance effect. This phenomenon is clearly observed in the unilateral capacitance–voltage (C–V) measurement. During the irradiation with a UV light source, holes are induced close to the electron injection location in Zn-rich bulk. These holes induced by UV light will cause barrier lowering effects and generate additional photocurrent under UV irradiation. The contrast current under UV light indicates that the on–off ratio between light-induced and dark current reaches 106 in dark conditions. In addition, this device has excellent light response and recovery speed in various light pulse environments. The high sensitivity and the high stability of this dual-active-layer UV light sensing TFT are beneficial to comprehensive and versatile applications in the semiconductor panel industry.