Thermal conductivity reduction in highly-doped cubic SiC by phonon-defect and phonon-electron scattering

We calculate the thermal conductivity (kappa) of highly N- and B-doped cubic silicon carbide (SiC) with defect concentrations (Cdef) from 1016 to 1021 cm-3 and compare the relative importance of the extrinsic phonon-electron and phonon-defect scattering mechanisms. Whereas phonon-electron scattering dominates over phonondefect scattering at low Cdef up to about 1020 cm-3 at room temperature in N-doped SiC, phonon-defect scattering determines the thermal conductivity reduction in the B-doped case. This strong contrast between the electron- and hole-doped cases is related to the much higher ionization energy of B acceptors as compared to that of N donors, and to the resonant scattering caused by B substitution, not present for the N impurity. The similar features can be found in hexagonal phase 4H-SiC. Our results highlight the importance of considering the phonon-electron scattering mechanism together with other phonon scattering processes when calculating the thermal conductivity of doped semiconductors.