Superior interfacial thermal conductance between β-Ga₂O₃ and diamond realized through metal-assisted epitaxial...

β-Ga₂O₃ exhibits great potential for next-generation power electronics, while its low thermal conductivity poses a challenge to efficient heat dissipation. We address this challenge by developing a gallium-assisted epitaxial strategy to synthesize highly oriented β-Ga₂O₃ film on diamond. The β-Ga₂O₃ presents a high thermal conductivity of 9.0 W m^-1 K^-1 and low thermal boundary resistance of 6.05 m² K GW^-1. In-situ experiments reveal a high interfacial bonding strength (>2.09 GPa), resulting from the atomically sharp and covalently bonded interface. The identified new interfacial phonon mode at ∼60 meV through the vibrational electron energy-loss spectroscopy can significantly enhance the phonon transport between diamond and β-Ga₂O₃. The developed gallium-assisted strategy may mitigate the thermal constraints of β-Ga₂O₃, offering a promising route for the heterointegration of β-Ga₂O₃-based power devices with diamond.