Impact of a process-induced interfacial layer on ferroelectric switching and reliability in AlScN/ β -Ga2O3 MFS capacitors

In this study, we demonstrate AlScN-based metal–ferroelectric–semiconductor capacitors directly integrated on a heteroepitaxial β-Ga2O3. Structural analysis reveals the presence of a process-induced amorphous intermixed layer at the AlScN/β-Ga2O3 interface. The fabricated devices exhibit ferroelectric switching behavior, characterized by counterclockwise hysteretic current–voltage loops with an on/off current ratio of >102, which is limited by the intermixed interfacial layer. Piezo-response force microscopy measurements confirm the intrinsic polarization switching capability through phase reversal and butterfly-shaped amplitude loops. Furthermore, positive-up-negative-down measurements indicate polarization switching while revealing a switching current asymmetry. We identify that this asymmetry originates from the internal electric field and charge trapping associated with the interfacial defect layer. This interfacial instability primarily affects the device performance observed during retention (103 s) and endurance (5 × 103 cycles) tests, suggesting significance of the interface toward stable ferroelectric operation in AlScN/β-Ga2O3 devices.