Effects of Li doping on the structural and electrical properties of solution-processed ZnO films for high-performance thin-film transistors

We report the structural and electrical properties of Li-doped ZnO (LZO) films, which are spin-coated via a simple solution process using Zn and Li precursor solutions. The Li doping improves the crystallinity of the ZnO films, and the LZO films exhibit a relatively dense and smooth surface morphology compared to that of the undoped ZnO films. Back-gated LZO thin-film transistors (TFTs) are fabricated onto a heavily p-doped Si substrate with a SiO2 gate dielectric, and operated in enhancement mode. In the case of the LZO TFT with a Li doping concentration of 0.50 mol%, the highest field-effect mobility of 5.18 cm2 V−1 s−1 is obtained; the on/off current ratio and subthreshold swing are 107 and 1.2 V dec−1, respectively. These results demonstrate that Li doping can effectively modulate the structural and electrical properties of ZnO-based films, facilitating the fabrication of LZO TFTs with enhanced performance.