Effect of Gd³⁺ Doping on Sol-Gel Prepared Y₂O₃ Films as Gate Insulators for Oxide Thin Film Transistors

The relationships between the microstructure and the dielectric properties of sol-gel prepared Y₂O₃ films with various Gd³⁺ doping were systematically investigated. Robust solution processed lanthanide films, (Y_1-Gd)₂O₃ (0 < x ≤ 0.5), are demonstrated as high-k gate insulators for low voltage-driven oxide thin film transistors and their optimized composition is presented. With the proper amount of Gd³⁺ doping, the corresponding thin film insulators exhibit low leakage current with increased dielectric constant. The resultant Zn-Sn-O/(Y, Gd)₂O₃ TFT exhibits enhanced performance, by a factor of 10.7 compared with TFTs using a SiO2 insulator, with a field-effect mobility of ~3.15 cm²V^-1s^-1 and an exceptionally low operating voltage <15 V.