Thermal Transport across Ion-Cut Monocrystalline β-Ga₂O₃ Thin Films and Bonded β-Ga₂O₃-SiC Interfaces

The ultrawide band gap, high breakdown electric field, and large-area affordable substrates make β-Ga₂O₃ promising for applications of next-generation power electronics, while its thermal conductivity is at least 1 order of magnitude lower than other wide/ultrawide band gap semiconductors. To avoid the degradation of device performance and reliability induced by the localized Joule-heating, proper thermal management strategies are essential, especially for high-power high-frequency applications. This work reports a scalable thermal management strategy to heterogeneously integrate wafer-scale monocrystalline β-Ga₂O₃ thin films on high thermal conductivity SiC substrates by the ion-cutting technique and room-temperature surface-activated bonding technique. The thermal boundary conductance (TBC) of the β-Ga₂O₃-SiC interfaces and thermal conductivity of the β-Ga₂O₃ thin films were measured by time-domain thermoreflectance to evaluate the effects of interlayer thickness and thermal annealing. Materials characterizations were performed to understand the mechanisms of thermal transport in these structures. The results show that the β-Ga₂O₃-SiC TBC values are reasonably high and increase with decreasing interlayer thickness. The β-Ga₂O₃ thermal conductivity increases more than twice after annealing at 800 °C because of the removal of implantation-induced strain in the films. A Callaway model is built to understand the measured thermal conductivity. Small spot-to-spot variations of both TBC and Ga₂O₃ thermal conductivity confirm the uniformity and high quality of the bonding and exfoliation. Our work paves the way for thermal management of power electronics and provides a platform for β-Ga₂O₃-related semiconductor devices with excellent thermal dissipation.