Phonon-electron scattering in single crystal silicon carbide

We have measured the thermal conductivity κ of single crystals of hexagonal silicon carbide (6H-SiC) of two different electron densities n. The densities are low such that virtually all of the heat is conducted by lattice vibrations. At low temperatures the thermal conductivity of both samples varies as T2 and scales with the electron density. The calculated phonon mean free path thus varies as T−1 and is consistent with a model of scattering of the heat-carrying phonons by electrons in an impurity band.