Photosensitivity of InZnO thin-film transistors using a solution process

Oxide semiconductor devices play a role in both switches and photo-sensors in interactive displays. During the fabrication of oxide semiconductor devices, the sol-gel solution process that is used to form an oxide semiconductor has various merits, including its simplicity and low cost as well as its good composition controllability. Here, we present the photosensitivity characteristics of an oxide photo thin-film transistor (TFT) created using the InZnO (IZO) sol-gel process. Upon exposure to light, photocurrent (I_photo) in the negative gate bias regime is significantly increased with a negligible threshold voltage shift. The photosensitivity is modulated by geometrical factors and by the IZO material composition. We observed a significant effect of the channel thickness and IZO composition on the photosensitivity, which was attributed to the screening effect of optically ionized oxygen vacancies (V_o⁺⁺). In particular, the optimized bi-layered oxide photo-TFT presents a good I_photo/I_dark photosensitivity value of 3 × 10⁴ and a subthreshold slope of 0.96 V/decade. In addition, the persistent photoconductivity of the oxide photo-TFT was removed by applying positive gate voltage, resulting in good high-speed operation. These results taken together demonstrate that the IZO photo-TFT produced by the sol-gel process can be workable when applied to interactive displays.