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

Because of its ultrawide bandgap, high breakdown electric field, and large area affordable substrates grown from the melt, beta 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 selfheating at high power, proper thermal management is even more essential for Ga2O3 devices. Similarly to the past approaches aiming to alleviate selfheating in GaN HEMTs, a possible solution has been to integrate thin Ga2O3 membranes with diamond to fabricate Ga2O3 on diamond lateral MESFET or MOSFET devices by taking advantage of the ultra high thermal conductivity of diamond. Even though the TBC between wide bandgap semiconductor devices such as GaN HEMTs 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 MWm2K1, 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 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 nanomembrane is also observed due to additional phonon membrane boundary scattering. The impact of the Ga2O3substrate TBC and substrate thermal conductivity on the thermal performance of a power device are modeled and discussed.