An Evaluation of Energy Transfer Pathways in Thermal Transport Across Solid/Solid Interfaces

Thermal transport across solid/solid interfaces has been extensively studied, but heat transfer pathways other than phonon transmission and electron-phonon nonequilibrium in the metal were usually neglected. In this work, we aim to build a general and unified model including both the above transport channels and others such as electron transmission and electron-interface coupling. For a general solid/solid system with electrons and phonons existing on both sides, an analytical solution to the interfacial thermal resistance is obtained. We show that the relative contribution from different transport channels depends on both the local condition at the interface and the bulk properties of each side of the interface. We find that for a metallic thin film deposited on a semiconductor substrate, the contribution of electron transmission to thermal transport is negligible when the semiconductor is not heavily doped even though the electronic interfacial thermal boundary resistance can be lower than the phononic counterpart at high temperatures. In contrast, the electron-interface channel plays an important role in the intrinsic to low-doped regime, where substrate phonons can remove heat efficiently from the interface.