Entropy production in hot-phonon energy conversion to electric potential

Abstract

We apply phonon and electron nonequilibrium-population statistical entropy analysis to the recently introduced phonon energy to electric potential conversion heterobarrier with its height optimized for optical phonon absorption under steady electric current. The entropy production rates for phonon and electron subsystems depend on their interaction kinetics and occupancy distributions, indicating the direction of the processes. Under upstream thermal equilibrium among electrons and acoustic and optical phonons, we predict an upper limit of 42% energy conversion for GaAs heterobarrier at 300 K, while the reported Monte Carlo prediction of 19% efficiency is below this limit. We show that for upstream electrons in thermal equilibrium with the acoustic phonons, while under supply of hot optical phonons, the conversion efficiency increases significantly, making integration of the barrier into optical phonon emitting circuits and devices very attractive.