Signatures of anharmonic phonon transport in ultrahigh thermal conductance across atomically sharp metal/semiconductor interface

The scatterings among the heat carriers at metal/semiconductor heterojunctions are important for the heat dissipation process in quantum information science systems. Phonon-phonon coupling at interfaces is accepted to be one of the main channels for thermal energy across the metal/semiconductor interface. Here, we show the thermal conductance across the metal/semiconductor interface, i.e., Al/Si interface, at room temperature is around 350 MW/m²K, which is 1.43 times higher than the harmonic limit and stems from the strong anharmonic phonon-phonon scatterings at the interface. The anharmonic phonon-phonon scatterings are found to benefit the interfacial thermal conductance from two mechanisms, i.e., the increase of the phonon occupation and inelastic phonon scattering channels. Our modal analysis suggests that the thermal conductance contributed by the interfacial vibrational modes is negligible, and the interfacial thermal transfer is dominated by the extended vibrational modes. By comparing our calculated thermal conductance with the experimental measurements, we find that electron-phonon coupling contributes ∼9% to the total interfacial thermal conductance, and the phonon-phonon coupling dominates the thermal transport across the interface. Our findings here have provided guidance for the thermal management design in the related quantum information electronics.