Research on the interface characteristics and leakage mechanisms of <b> <i>β</i> </b>-Ga2O3 MFIS capacitors using an HfO2–ZrO2 superlattice layer

This letter reports the fabrication and characterization of β−Ga2O3 metal/ferroelectric/insulator/semiconductor (MFIS) capacitors employing 3 types of HfO2–ZrO2 superlattice (SL) ferroelectric gate dielectrics: SL5, SL10, and SL15, constructed by alternating 5,10, and 15 ALD cycles of HfO2 and ZrO2, respectively, with conventional Hf0.5Zr0.5O2 (HZO) as a reference. Following rapid thermal annealing (RTA) at 550 °C for 30 s, all dielectrics are confirmed to exhibit the orthorhombic (111) phase by grazing-incidence x-ray diffraction (GIXRD). Electrical measurements reveal that the SL5 structure achieves an outstanding reduction in leakage current, decreasing from 0.936 A cm−2 (HZO) to 0.004 A cm−2 at 3 V, and exhibits the highest remanent polarization (2Pr = 29.3 μC cm−2), compared to 27.3 μC cm−2 (HZO), 22.4 μC cm−2 (SL10), and 17 μC cm−2 (SL15). Moreover, the SL5 capacitor demonstrates excellent reliability, maintaining robust endurance up to 1 × 1011 cycles at room temperature and 1 × 1010 cycles at 150 °C without degradation and stable retention over 1 × 104 s. Importantly, interface state analysis reveals that after annealing, SL5 maintains the lowest and most stable interface trap density within the energy range of 0.25–0.45 eV. The trap state density (6.39 × 1012–7.11 × 1012 cm−2 eV−1) is significantly lower than that of HZO in the same energy range. These results highlight the advantages of superlattice-engineered ferroelectric gate dielectrics for achieving high-quality interfaces, low leakage current, and stable ferroelectric performance, providing a promising route toward high-performance, enhancement-mode β−Ga2O3 MOSFET devices for next-generation power electronics.