Oxide semiconductor thin-film transistors with nano-splitting and field-surrounding channels fabricated by subwavelength photolithography

Abstract

Oxide semiconductors feature high tunability of carrier concentrations under the control of electric field. In thin film transistors (TFTs), applying dual gate has been reported to be efficient in enhancing the coupling between the gate field and the channel accumulation. In this work, we demonstrate nano-splitting and field-surrounding semiconducting channels (based on InGaZnO) in TFTs, which is fabricated by facile subwavelength photolithography. In such TFTs, semiconducting channels have 200 nm gaps parallel to the drain field, are wrapped by oxide insulators and thus the gate field. The devices show enhanced performance as compared with dual-gate and single gate TFTs, exhibiting higher drain current and steeper subthreshold swing. The maximum transconductance gm is 27.9% higher than dual gate TFT and 73.1% higher than single gate TFT. According to device simulation, the improvement of the wrapping insulators device correlates with the three-dimensional accumulation of carriers and increased gate electric field near the semiconductor-dielectric interface. These surrounded-channel effects become noticeable in the device with the gap distance less than 1 μm, with gate electric field squeezing in the submicron gaps. The proposed approach offers an alternative way to take advantage of the oxide semiconductors and their application in TFTs with related circuits.