Mechanism of Improving Al₂O₃/β-Ga₂O₃ Interface After Supercritical Fluid Process at a Low Temperature

β -Ga₂O₃, a wide bandgap semiconductor, has gained attention for its high breakdown voltage and fast switching properties. However, challenges exist because of high interface densities at the Al₂O₃/β -Ga₂O₃ interface, which greatly impacts the performance and reliability of metal-oxide-semiconductor field-effect transistor (MOSFET) devices. As a low-temperature solution, the supercritical fluid process (SCFP) is introduced to the fabrication process of Al₂O₃/β -Ga₂O₃ metal-oxide-semiconductor capacitor (MOSCAP), which effectively reduces the oxygen vacancies and interface defects, in particular avoiding the damage to the materials caused by high temperature. The near-interface traps are decreased by two times, and the interface states are reduced by five times. As a result, the breakdown electric field is improved from 6.01 to 8.47 MV cm^-1. The mechanism of the SCFP is explored and explained by using different measurement and analysis methods. Deep-level transient spectroscopy (DLTS) results indicate that the defect concentration of SCFP devices decreases and the electron capture interface increases. Supercritical fluid treatment can passivate the traps by reducing O vacancies in the Al₂O₃. The study concludes that the proposed SCFP significantly improves the dielectric/semiconductor interface, which can greatly enhance the performance of transistors.