Extremely high photoconductivity ultraviolet-light sensor using amorphous In-Ga-Zn-O thin-film-transistor

Abstract

An amorphous (alpha) indium-gallium-zinc-oxide (IGZO) thin-film-transistor (TFT) was developed as a precise ultraviolet-light (UV-light) sensor, which is extremely sensitive to photoconductivity. A higher absorption of UV-light via a longer UV-light irradiation time and a higher UV-light intensity shifted the threshold voltage (V-th) to a negatively higher voltage and then saturated above a specific UV-light irradiation time. Particularly, the photoconductivity (i.e., V-th) shifts were evidently dependent on the oxygen vacancy (V-O)-induced defect density of an ALD alpha-IGZO channel; in turn, a higher V-O-induced defect density led to a higher photoconductivity shift. Additionally, the V-th saturation time in an ALD alpha-IGZO TFT decreased rapidly with increasing UV-light intensity; in particular, a higher V-O-induced defect density presented a smaller decay constant of the V-th saturation time. Furthermore, the V-th after stopping the UV-light irradiation was rapidly recovered to the condition as without UV-light irradiation condition and a higher V-O-induced defect density exhibited a longer recovery time.