Resonant phonon scattering in semiconductors

Boron impurities have recently been shown to induce resonant phonon scattering in 3C-SiC, dramatically lowering its thermal conductivity. The B-doped 3C-SiC is associated with an off-center relaxation of the B atom, inducing a local transition from T-d to C-3v symmetry. Similar relaxations in B and N-doped diamond, with a similarly large effect on the interatomic force constants (IFCs), fail to produce resonances. Here we develop an intuitive understanding of such dopant-induced resonant phonon scattering in semiconductors with the help of a 1D monoatomic chain model. We find that the phenomenon is connected to a slight asymmetry in the relaxed position of the defect, with its origin in two or more minima of the potential energy surface in close proximity. The large perturbation they introduce in the IFCs is the essential ingredient of a resonance.