Thermal Conductivity ofn-Type Germanium from 0.3 to 4.2 K

Abstract

The thermal conductivity of lightly Sb-, P-, and As-doped germanium was measured between 0.3 and 4.2 K. The strong scattering of phonons by neutral donors observed earlier above 1 K diminishes below 1 K, as predicted by the theories of Keyes and of Griffin and Carruthers. Inclusion of resonance fluorescence of phonons, as proposed by Griffin and Carruthers, improves agreement with the measured thermal conductivity (except at the lowest temperatures, where neither their theory nor that of Keyes fits the data very well) and leads to the value 16 eV for the deformation potential and to simple-hydrogenic-model values for the effective radii of the donor ground states. The divergence of the data from the calculated values at the lowest temperatures is evidence for an additional scattering mechanism effective below 1 K, possibly associated with phonon-assisted hopping between donor atoms.