Solution processed rare-earth doped high-k dielectrics for low-power IGZO transistors

Low-power metal oxide transistors are highly required in displays, logic circuit and sensors. High quality gate dielectrics with the properties of high dielectric constant, smooth surface, and excellent insulating performance are critical to realize the above mentioned transistors. In this work, we present a universal strategy by using rare-earth (RE) elements (Y, Er and Yb) as dopants to improve the dielectric properties of zirconia film for low-power transistors. Additionally, all the dielectric films are prepared by solution process, which is compatible with low-cost and large-area manufacturing technology. The leakage current densities of zirconia films decrease from 1.27 × 10⁻⁵ A/cm² to 2.8 × 10⁻⁷ A/cm², 6.6 × 10 − 7 A/cm², and 4.3 × 10⁻⁷ A/cm² by doping a small amount of Y, Er, and Yb in zirconia films, respectively. Furthermore, bottom-gate top-contact indium-gallium-zinc oxide (IGZO) transistors with RE-doped zirconia dielectrics show one order improved current on/off (∼10⁴) ratio and achieve one order improvement in mobility (3.11, 2.85, 2.75 cm²V⁻¹S⁻¹ for Y-, Er-, Yb-doped devices respectively) compared with that of pure zirconia film based devices (0.30 cm²V⁻¹S⁻¹). Moreover, the subthreshold swing (SS) of TFTs based on RE-doped and undoped ZrO₂ dielectric films are calculated (0.2, 0.36, 0.21 V/dec for Y-, Er-, Yb-doped devices respectively, and 0.51 V/dec for undoped devices) This study demonstrates the validity of RE ions as dopants in gate dielectrics to achieve high-performance low-power metal oxide transistors.