Phonon-drag effects on thermoelectric power

TL;DR

This paper develops a new theoretical approach to calculate the phonon-drag contribution to thermoelectric power in semiconductors and quantum wells, accounting for various temperature regimes and phonon interactions.

Contribution

It introduces an extended balance equation transport theory for phonon-drag effects applicable across temperature ranges, including hot-electron conditions.

Findings

The theory matches experimental data across temperature regimes.

Phonon-drag significantly influences thermoelectric power in hot-electron transport.

The approach accounts for wavevector and phonon-mode dependent relaxation times.

Abstract

We carry out a calculation of the phonon-drag contribution $S_g$ to the thermoelectric power of bulk semiconductors and quantum well structures for the first time using the balance equation transport theory extended to the weakly nonuniform systems. Introducing wavevector and phonon-mode dependent relaxation times due to phonon-phonon interactions, the formula obtained can be used not only at low temperatures where the phonon mean free path is determined by boundary scattering, but also at high temperatures. In the linear transport limit, $S_g$ is equivalent to the result obtained from the Boltzmann equation with a relaxation time approximation. The theory is applied to experiments and agreement is found between the theoretical predictions and experimental results. The role of hot-electron effects in $S_g$ is discussed. The importance of the contribution of $S_g$ to thermoelectric power in the hot-electron transport condition is emphasized.