Solution-Processed Aluminum-Zirconium Oxide as a Gate Dielectric for InGaZnO Thin Film Transistors

This study presents a solution-processed aluminum-zirconium oxide (AlZrO_x) dielectric for amorphous indium-gallium-zinc oxide (a-IGZO) thin-film transistors (TFTs). Solution-processed AlZrO_x thin films exhibit overall improved dielectric properties, such as leakage current characteristics of 1.10 × 10^–8 A/cm² at 0.5 MV/cm and high dielectric constants of approximately 9.1 by combining the advantages of aluminum oxide (AlO_x) and zirconium oxide (ZrO_x). Solution-processed IGZO TFTs using the AlZrO_x film as a gate insulator layer exhibited a threshold voltage of 0.64 V, field-effect mobility of 3.06 cm²/V s, and a subthreshold slope of 0.26 V/dec. In addition, the IGZO TFTs with the AlZrO_x films exhibited a higher on/off current ratio of 1.05 × 10⁶ than devices with the AlO_x and ZrO_x gate insulator layers. The improvement of device properties is mainly attributed to the interface properties. The IGZO TFTs with the AlZrO_x gate insulator exhibited the lowest interface trap density of 2.07 × 10¹² cm⁻² eV⁻¹, compared to the devices with the AlO_x and ZrO_x gate insulators of 3.30 × 10¹² and 5.06 × 10¹² cm⁻² eV⁻¹, respectively, because of the smooth surface roughness and reduced residual hydroxyl groups in the films. The IGZO TFTs with the AlZrO_x gate insulator also improved hysteresis characteristics with the hysteresis window of 0.17 V. This study presents a significant step toward developing low-cost, low-power-consumption, and high-performance oxide electronic device.