In order to investigate the performance of ZnO-based thin film transistors (ZnO-TFTs), we fabricate devices using amorphous hafnium dioxide (HfO2) high-k dielectrics. Sputtered ZnO was used as the active channel layer, and aluminium source/drain electrodes were deposited by thermal evaporation, and the HfO2 high-k dielectrics are deposited by metal-organic chemical vapour deposition (MOCVD). The ZnO-TFTs with high-k HfO2 gate insulators exhibit good performance metrics and effective channel mobility which is appreciably higher in comparison to SiO2-based ZnO TFTs fabricated under similar conditions. The average channel mobility, turn-on voltage, on-off current ratio and subthreshold swing of the high-k TFTs are 31.2 cm2V-1s-1, -4.7 V, ~103, and 2.4 V/dec respectively. We compared the characteristics of a typical device consisting of HfO2 to those of a device consisting of thermally grown SiO2 to examine their potential for use as high-k dielectrics in future TFT devices.
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Ngwashi, K.D., Cross, B.M.R., Paul, S. et al. High Mobility ZnO thin film transistors using the novel deposition of high-k dielectrics. MRS Online Proceedings Library 1315, 618 (2011). https://doi.org/10.1557/opl.2011.721