Performance improvements of ZnO thin film transistors with reduced graphene oxide-embedded channel layers

ZnO thin film transistors (TFTs) with reduced graphene oxide (RGO)-embedded channel layers were fabricated and their electrical properties were compared with those of ZnO TFTs with no embedded layer (bare ZnO TFT), with Cr-embedded channel layers, and with a RGO/ZnO bilayer channel. Compared to the reference samples, the proposed ZnO TFTs with RGO-embedded layers exhibited very stable unipolar transfer characteristics with enhanced carrier mobility of 1.13 cm² V⁻¹ s⁻¹, subthreshold swing of 0.53 V decade⁻¹, and on/off ratio of 2.31 × 10⁷, unlike most previous reports of graphene-embedded ZnO TFTs which exhibited undesirable ambipolar behavior. These improvements are attributed to the high carrier mobility of the RGO layer and the formation of the ZnO-RGO-ZnO area as a leakage prevention barrier in the negative bias region. In addition, through X-ray photoelectron spectroscopy analysis, it was found that the formation of Zn–C bonds allows for the stable operation of the proposed RGO-embedded ZnO TFT. These results will provide important information for the design of high-mobility TFT architectures for various applications.