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

The ultrawide band gap, high breakdown electric field, and large-area affordable substrates make β-GaO 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-GaO 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-GaO-SiC interfaces and thermal conductivity of the β-GaO 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-GaO-SiC TBC values are reasonably high and increase with decreasing interlayer thickness. The β-GaO 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 GaO 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-GaO-related semiconductor devices with excellent thermal dissipation.