Effective Suppression of MIS Interface Defects Using Boron Nitride toward High-Performance Ta-Doped-β-Ga₂O₃ MISFETs

β-Ga₂O₃ is considered an attractive candidate for next-generation high-power electronics due to its large band gap of 4.9 eV and high breakdown electrical field of 8 MV/cm. However, the relatively low carrier concentration and low electron mobility in the β-Ga₂O₃-based device limit its application. Herein, the high-quality β-Ga₂O₃ single crystal with high doping concentration of ∼3.2 × 10¹⁹ cm^-3 was realized using an optical float-zone method through Ta doping. In contrast to the SiO₂/β-Ga₂O₃ gate stack structure, we used hexagonal boron nitride as the gate insulator, which is sufficient to suppress the metal-insulator-semiconductor (MIS) interface defects of the β-Ga₂O₃-based MIS field-effect transistors (FETs), exhibiting outstanding performances with a low specific on-resistance of ∼6.3 mΩ·cm², a high current on/off ratio of ∼10⁸, and a high mobility of ∼91.0 cm²/(V s). Our findings offer a unique perspective to fabricate high-performance β-Ga₂O₃ FETs for next-generation high-power nanoelectronic applications.