Thermal conductance across β-Ga2O3-diamond van der Waals heterogeneous interfaces

Because of its ultra-wide bandgap, high breakdown electric field, and large-area affordable substrates grown from the melt, β-Ga2O3 has attracted great attention recently for potential applications of power electronics. However, its thermal conductivity is significantly lower than those of other wide bandgap semiconductors, such as AlN, SiC, GaN, and diamond. To ensure reliable operation with minimal self-heating at high power, proper thermal management is even more essential for Ga2O3 devices. Similar to the past approaches aiming to alleviate self-heating in GaN high electron mobility transistors, a possible solution has been to integrate thin Ga2O3 membranes with diamond to fabricate Ga2O3-on-diamond lateral metal-semiconductor field-effect transistor or metal-oxide-semiconductor field-effect transistor devices by taking advantage of the ultra-high thermal conductivity of diamond. Even though the thermal boundary conductance (TBC) between wide bandgap semiconductor devices and a diamond substrate is of primary importance for heat dissipation in these devices, fundamental understanding of the Ga2O3-diamond thermal interface is still missing. In this work, we study the thermal transport across the interfaces of Ga2O3 exfoliated onto a single crystal diamond. The van der Waals bonded Ga2O3-diamond TBC is measured to be 17 −1.7/+2.0 MW/m2 K, which is comparable to the TBC of several physical-vapor-deposited metals on diamond. A Landauer approach is used to help understand phonon transport across a perfect Ga2O3-diamond interface, which in turn sheds light on the possible TBC one could achieve with an optimized interface. A reduced thermal conductivity of the Ga2O3 nano-membrane is also observed due to additional phonon-membrane boundary scattering. The impact of the Ga2O3–substrate TBC and substrate thermal conductivity on the thermal performance of a power device is modeled and discussed. Without loss of generality, this study is not only important for Ga2O3 power electronics applications which would not be realistic without a thermal management solution but also for the fundamental thermal science of heat transport across van der Waals bonded interfaces.