Effect of electron-phonon interaction on lattice thermal conductivity of SiGe alloys

While it is well-known that electron-phonon scattering often determines the electron mobility, its impact on lattice thermal conductivity is less clear. Dominant phonon scattering mechanisms that determine the lattice thermal conductivity have been attributed to phonon-phonon and phonon-defect interactions. However, recent studies in silicon have shown that strong electron-phonon interaction can also lead to significant phonon scatterings at high carrier concentrations. Here, we use first-principles simulations to study thermal transport in SiGe alloys and show that the effect of electron-phonon interaction on thermal transport is even more significant than that in Si because mass disorder scattering leaves long mean free path phonons behind, which are more strongly scattered by electrons. At the carrier concentration of 1 × 1020 cm−3, the room temperature lattice thermal conductivity of the Si0.9Ge0.1 alloy including electron-phonon interaction is only 40% of the value without this interaction. The results show that thermal transport in alloys at a high doping level can be significantly impacted by the free carriers, providing important insights into heat conduction mechanisms in thermoelectric materials which are mostly based on heavily doped alloys.