Hydrophilic bonding of β-Ga₂O₃ with diamond membranes

Diamond provides β-Ga2O3 power electronic devices with the much-desired p-type doping capability and enhancement in heat dissipation. This work reports on a hydrophilic bonding process to construct β-Ga2O3/diamond heterojunctions using polycrystalline diamond membranes grown on Si substrates. This method not only circumvents the challenges of direct diamond growth on β-Ga2O3 but also is distinct from the mainstream β-Ga2O3/diamond bonded heterostructures by being readily scalable to large wafers. A mesa–trench network etched in the β-Ga2O3 was developed to effectively remove voids and fluid pockets generated during the bonding of planar structures. Electron microscopies confirmed that the bonding interface was without gaps or voids. Energy-dispersive x-ray spectroscopy revealed insignificant interdiffusion of chemical elements across the interface, as expected of the low-temperature hydrophilic bonding process. A thermal boundary conductance of 65 MW/m2∙K, measured using the frequency-domain<br/>thermoreflectance technique, is one of the highest achieved for β-Ga2O3/diamond heterostructures.