Universal Way to Enhance Solution-Processed High-κ Oxide Dielectrics Performance by Sulfate Incorporation

Vacuum-free, solution-processable high-κ-oxide dielectrics are considered to be a key element for emerging low-cost flexible electronics. However, they usually suffer from low breakdown strength and frequency-dependent capacitance, which limit their broader applications. Here, we report a universal way to improve solution-based high-κ oxide dielectric properties (e.g., Al₂O₃, ZrO₂, Ga₂O₃, Sc₂O₃, Ho₂O₃, and Sm₂O₃) by sulfate incorporation. In-depth characterization shows that sulfate incorporation could reduce hydrogen and oxygen vacancy-related defects in high-κ oxides, thereby improving the dielectric performance. The optimized S-doped high-κ oxides show smooth surface (rms < 0.20 nm), low leakage current (∼10^-7 A/cm²@4 MV/cm), excellent dielectric breakdown strength (>10 MV/cm), and stable capacitance-frequency characteristics. Besides, oxide thin-film transistors based on these high-κ dielectrics exhibit excellent performance (e.g., mobility >20 cm² V^-1 s^-1, on/off ratio of ∼10⁷, threshold swing of ∼0.14 V dec^-1, threshold voltage of ∼0 V, and hysteresis of ∼0.02 V). Thus, this work provides a general approach for the development of high-quality solution-based high-κ oxides for transistor circuitry.