Improved Interface Quality in β -Ga 2 O 3 MOSFETs With a Crystalline (AlGa) 2 O 3 Cap

This work demonstrates$\beta $-Ga2O3 metal-oxide-semiconductor (MOS) devices with a crystalline (AlGa)2O3 cap formed by thin Al2O3 predeposition and postdeposition annealing (PDA). The cap effectively passivates interface defects and improves the overall gate-stack quality. Compared with control devices, the capped$\beta $-Ga2O3 MOS field-effect transistors (MOSFETs) show reduced hysteresis, improved subthreshold swing, enhanced current density, loweroff-state leakage, and improved breakdown, yielding a 42.7% enhancement in power figure of merit (PFOM). Reduced threshold-voltage shift under positive gate-bias stress further confirms suppressed electron trapping, highlighting crystalline (AlGa)2O3 cap engineering as an effective approach for improving$\beta $-Ga2O3 MOS interface quality and device performance.