The lifetimes of quantum excitations are directly related to the electron and phonon energy linewidths of a particular scattering event. Using the versatile double time thermodynamic Green’s function approach based on many-body theory, an ab-initio formulation of relaxation times of various contributing processes has been investigated with newer understanding in terms of the linewidths of electrons and phonons. The energy linewidth is found to be an extremely sensitive quantity in the transport phenomena of crystalline solids as a collection of large number of scattering processes, namely, boundary scattering, impurity scattering, multiphonon scattering, interference scattering, electron–phonon processes and resonance scattering. The lattice thermal conductivities of three samples of GaAs have been analysed on the basis of modified Callaway model and a fairly good agreement between theory and experimental observations has been reported.

The phenomenon of heat conduction is important in semiconductor devices. This property is investigated on the basis of modified Callway model. The formalism was carried out using Hamiltonian, phonon Green’s function and equation of motion techniques for various scattering events. It was found that every scattering mechanism is independent of each other and does not affect the others. The thermal conductivity of lead sulphide (PbS) semiconductor has been studied on the basis of this concept. The results of the present model are in good agreement with experimental results and the model shows good future scope with other semiconductors and superconductors.