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 AlO x /AZO nanoparticles/SiO 2 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 lightassisted detrapping charges. The methodology used in this study provides a unique approach to achieve photosensitive and photostable duality within a single device.
Charge-trapping memories (CTMs) based on zinc tin oxide (ZTO) semiconductor thin-film transistors (TFTs) can be programmed by a positive gate voltage and erased by a negative gate voltage in conjunction with light illumination. To understand the mechanism involved, the sub-gap density of states associated with ionized oxygen vacancies in the ZTO active layer is extracted from optical response capacitance–voltage (C–V) measurements. The corresponding energy states of ionized oxygen vacancies are observed below the conduction band minimum at approximately 0.5–1.0 eV. From a comparison of the fitted oxygen vacancy concentration in the CTM-TFT after the light-bias erasing operation, it is found that the pristine-erased device contains more oxygen vacancies than the program-erased device because the trapped electrons in the programmed device are pulled into the active layer and neutralized by the oxygen vacancies that are present there.
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