Low-Leakage and Low-Voltage Rare-Metal-Free TFTs Using Solution Combustion-Synthesized Al2O3 Dielectrics

Abstract Integrating high-κ dielectrics is essential for achieving low-voltage operation in cost-effective solution-processed thin-film transistors. However, solution-processed dielectrics often exhibit high leakage due to incomplete metal oxide stoichiometry and inherent film impurities. Here, we demonstrate a low-leakage and low-voltage SixSnyO TFT using a combustion-assisted Al2O3 dielectric. Previous reports on solution-processed Al2O3 thin films often faced challenges regarding film quality and dielectric performance, frequently exhibiting leakage currents in the microampere range. To overcome these issues, we established optimal parameters of Al2O3 preparation via solution combustion synthesis. Solution combustion synthesis is unique and beneficial because the exothermic heat of combustion promotes metal oxide formation, thereby improving the conventional sol-gel method for producing thin films. Through optimization, we confirmed that 0.10 M is the most suitable Al3+ concentration, producing films with good surface roughness and high bulk density. Additionally, stacking Al2O3 films via multilayer spin-coating yielded a denser film, resulting in a leakage current density of approximately 6.0 nA/cm2 at 2.0 MV/cm and a breakdown field of approximately 3.6 MV/cm. Overall, the film produced using 0.10 M and 3 layers exhibited better quality with fewer trap states. Moreover, despite a thickness of approximately 30 nm, the leakage current rivals that of other vacuum-processed Al2O3 films. Using this dielectric, SixSnyO TFTs were fabricated and exhibited excellent TFT performance: μlin = 2.76 cm2/(V·s), VON = 0.27 V, ION/IOFF = 3.4 × 105, and SS = 0.23 V/dec.