Molecular beam epitaxy of ferroelectric ScAlN on β -Ga2O3 substrates

We demonstrate the epitaxial integration of ferroelectric ScAlN thin films on β-Ga2O3 substrates via molecular beam epitaxy without any buffer layers, enabled by surface pre-nitridation. The resulting ScAlN films exhibit robust ferroelectricity, characterized by large apparent remanent polarization (>150 μC/cm2), good retention (>105 s), and minimal fatigue observed up to 105 switching cycles. High-resolution x-ray photoelectron spectroscopy reveals a type-II band alignment at the ScAlN/β-Ga2O3 heterointerface, with extracted valence and conduction band offsets of 0.5 and 1.0 eV, respectively. These results establish an oxide/nitride heterostructure platform that combines the intrinsic ferroelectricity of ScAlN with the ultra-wide bandgap and photosensitive properties of β-Ga2O3, offering compelling opportunities for next-generation nonvolatile memory, photodetection, and optoelectronic synaptic devices.