Thermoelectric figure of merit enhancement in dissipative superlattice structures

Abstract

Utilizing the non-coherent quantum transport formalism, we investigate thermoelectric performance across dissipative superlattice configurations in the linear regime of operation. Using the {\it{dissipative}} non-equilibrium Green's function formalism coupled self-consistently with the Poisson's equation, we report an enhanced figure of merit $zT$ in the multi-barrier device designs. The proposed enhancement, we show, is a result of a drastic reduction in the electronic thermal conductance triggered via non-coherent transport. We show that a maximum $zT$ value of 18 can be achieved via the inclusion of non-coherent elastic scattering processes. There is also a reasonable enhancement in the Seebeck coefficient, with a maximum of $1000~\mu V/K$, which we attribute to an enhancement in electronic filtering arising from the non-coherent transport. Distinctly the thermal conduction is drastically reduced as the length of the superlattice scales up, although the power factor shows an overall degradation. While the presence of interfaces is known to kill phonon thermal conduction, our analysis shows that non-coherent processes in superlattice structures can effectively kill electronic thermal conduction also. We believe that the analysis presented here could set the stage to understand better the interplay between non-coherent scattering and coherent quantum processes in the electronic engineering of heterostructure thermoelectric devices.