Cooling gallium oxide electronics with cubic boron arsenide

Gallium oxide (Ga₂O₃) power electronics are hindered by a significant thermal bottleneck arising from its low and anisotropic thermal conductivity. To address this challenge, we propose a cooling strategy through the heterogeneous integration with cubic boron arsenide (cBAs), an emerging material with an ultrahigh thermal conductivity κ of ~1300 Wm^-1K^-1. Our computational analysis based on machine-learned nonequilibrium molecular dynamics reveal remarkable interfacial thermal conductance G especially with Ga-As and O-B bonding across the interface, with values up to ~750 MWm^-2K^-1 at 300 K. The underlying mechanism is attributed to the well-matched phonon density of states between β-Ga₂O₃ and cBAs, facilitated by their comparable Debye temperatures. Furthermore, our device-level modeling confirms cBAs integration leads to a superior temperature reduction, surpassing conventional substrates including diamond. This study underscores the simultaneously ultrahigh κ and G of cBAs as an ideal substrate for Ga₂O₃ electronics.