THE EFFECT OF NONMETAL-METAL TRANSITION DUE TO DOPING ON LATTICE THERMAL CONDUCTIVITY : APPLICATION TO Ge-DOPED InSb

Abstract
In this work we explain the phonon thermal conductivity results of Ge-doped InSb from 2 to 50 K for impurity concentrations 7.2x10¹⁷ and 5.0x10¹⁷ cm^-3. Since these lie in the intermediate concentration region of the metal-nonmetal transition the theory of scattering of phonon by holes in the mixed state, i.e. both in the localised non-metallic and in the metallic state is used. The hole concentrations in the non-metallic and metallic regions are calculated for each sample by using Mikoshiba's inhomogeneity model, the theory of both bound hole-phonon and free hole phonon scattering are applied to explain the results. The value of density-of-states effective mass are kept constant (=0.23) with the variation in temperature. The value of the dilatation and shear deformation potential constants obtained from our calculations are in good agreement with previously determined values. The effect of impurity scattering due to doped impurities along with isotope scattering is also taken into account. It is reported that in the intermediate concentration range, the mixed hole-phonon scattering must be included to explain the temperature dependence of thermal conductivity of Ge-doped InSb.