Deep-ultraviolet sensing characteristics of transparent and flexible IGZO thin film transistors

Abstract

Recently, deep-ultraviolet (DUV) photodetectors with useful functions including transparency and flexibility have been developed for a real-time environmental monitoring, a wearable monitoring system, transparent wireless communication, and a smart window system. In this study, we investigate the DUV sensing characteristics of transparent and flexible IGZO thin-film transistors (TFTs) fabricated by a dry transfer printing, which is a very promising technique affording the device fabrication on unconventional surfaces. The fabricated TFT devices show high mechanical stability even at a bending radius of 1.4 mm, and the repeatable and gate bias-dependent DUV photoresponse characteristics. The gate bias-dependent photocurrent (Iph) decay characteristics are likely attributed to the different surface re-adsorption rates of oxygen molecules depending on the gate bias polarity, which are qualitatively described based on energy band diagrams. In addition, the wavelength-dependent photoresponse characteristics of the IGZO TFT device upon UV illumination with λ = 245 nm show a 10 times faster Iph decay behavior than that upon UV illumination with λ = 365 nm. The result implies that the dissociative oxygen arising from the DUV illumination could accelerate the Iph decay due to the increased surface adsorption.