Electronic contribution to the thermal conductivity of narrow band gap semiconductors-effect of non-parabolicity of bands

A theoretical calculation of the electronic contribution to the thermal conductivity ( lambda e ) of narrow band gap semiconductors is presented which takes into account the non-parabolic nature and multivallied structure of the energy bands including intervalley scattering. The analysis indicates a significant reduction in the Lorenz factor L and the ratio of electronic and lattice thermal conductivities ( lambda e / lambda L ) when non-parabolicity of the bands is taken into consideration. The case of lead telluride is studied in more detail and a semiquantitative agreement sought between the theoretical and experimental values. Scattering of carriers by acoustic phonons and by polar optical phonons has been considered.