Phonon-drag effects on thermoelectric power

We carry out a calculation of the phonon-drag contribution Sg to the thermoelectric power of bulk semiconductors and quantum well structures using the balance equation transport theory extended to weakly nonuniform systems. Introducing temperature-, wave-vector-, and mode-dependent phonon relaxation times due to phonon-phonon interactions, our formulation can be used not only at low temperatures where the phonon mean free path is determined by boundary scattering, but also at high temperatures. Our analysis of the role of the phonon relaxation times in regard to dependencies on temperature, wave vector, and mode provides results for the linear thermoelectric power Sg which are in agreement with experimental data over a broad range of densities and temperatures. {} 1996 The American Physical Society.