Charge Trapping Augmented Switchable Sub-band-gap Photoresponse of Zinc-Tin Oxide Thin-Film Transistor

In this study, a charge trapping thin-film transistor (TFT) is demonstrated based on a zinc-tin oxide (ZTO) semiconductor channel layer and a stack of AlOx/AZO nanoparticles/SiO2 as the gate dielectrics. This device can be switched from the pristine state to the charge trapping state via the application of a positive gate voltage pulse (V-G = 40 V for 1 s). When the TFT is set at the charge trapping state, the dynamic photoresponse (to light in the wavelength of 405 or 635 nm) of drain current gain can be significantly enhanced as compared to that of the device set at the pristine state. As a comparison, the ZTO TFT without the nanoparticulate AZO layer exhibits neither charge trapping nor enhanced photoresponse characteristics. The enhancement in the dynamic photoresponse of the charge trapping TFT is attributed to the increasing number of electrons at the ZTO channel by light-assisted detrapping charges. The methodology used in this study provides a unique approach to achieve photosensitive and photostable duality within a single device.