Reduced Thermal Conductivity in SiGe Alloy-Based Superlattices for Thermoelectric Applications

In this paper, we demonstrate the sensitivity of the lattice thermal conductivity in SLs to the interface properties, based on solving the phonon Boltzmann transport equation under the relaxation time approximation. Previous calculations relied on treating the interface scattering with an empirical specularity parameter, which is then adjusted to fit measured data. In this work, in order to accurately treat phonon scattering from a series of rough interfaces with a given rms roughness height (Δ), we employ a momentum-dependent specularity parameter p(q) that is the fraction of specular reflections to the total number of reflections from a rough boundary (0 ≤ p(q⃗) ≤ 1).