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

<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula>-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/<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula>-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/<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula>-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.