Thermal transport in ion-beam-exfoliated β-Ga₂O₃ nanomembranes

β-Ga₂O₃ is a promising material for power electronics due to its wide bandgap and high breakdown field, but its low thermal conductivity poses challenges for heat dissipation. To address this, we employed ion beam exfoliation to fabricate β-Ga₂O₃ nanomembranes integrated with highly thermally conductive Si substrates. To do this, chromium ion implantation was used to induce stress and strain, forming rolled-up microtubes on (100)-oriented β-Ga₂O₃ single crystals. After successfully transferring these tubes onto Si substrates and performing thermal annealing, these microtubes were unrolled into nanomembranes. X-ray diffraction and Raman measurements revealed the high quality of the samples. Time-domain thermoreflectance was used to study thermal transport in these structures, confirming uniform thermal conductivity across three fabricated samples. A Debye-based thermal transport model was implemented to validate experimental results and define the main phonon scattering mechanisms. Non-equilibrium molecular dynamics simulations revealed that a thin amorphous SiO₂ interlayer significantly enhanced the thermal boundary conductance (TBC) across the β-Ga₂O₃/Si interface by bridging the vibrational mismatch between β-Ga₂O₃ and Si. However, further increasing the interlayer thickness led to phonon scattering and reduced TBC, emphasizing the importance of precise interface thickness control. This study highlights ion beam exfoliation as a scalable approach for integrating β-Ga₂O₃ with thermally conductive substrates, providing a pathway to improved thermal management in β-Ga₂O₃-based power electronics.