Solution-processed high-mobility ZnO thin film transistors based on multiple-stacked channel layer doped with Hf and Mg

We report solution-processed high-mobility ZnO thin film transistors (TFTs) obtained by inserting multiple-stacked channel layers comprising two layers of ZnO/Hf-doped ZnO and three layers of ZnO/Mg-doped ZnO/Hf-doped ZnO. The mobility of the thus-prepared TFTs was enhanced compared to a single layer of undoped ZnO and Mg-/Hf-doped ZnO. The TFTs prepared by double- and triple-stacked channels exhibited excellent electrical performances with high field-effect mobilities of 36.0 and 71.9 cm2 V−1s−1, respectively, and high on/off current ratios of the order of 107. X-ray photoelectron spectroscopy and transmittance measurements suggest that the double- and triple-stacked channel layers composed of undoped ZnO and ZnO matrix doped with Hf and Mg could provide suitable charge carriers and reduce the trap state at the interfaces.