Thermoelectric transport in periodic one-dimensional stacks of InAs/GaAs quantum dots

Abstract

We investigate the effect of the narrow electronic minibands of periodic one-dimensional stacks of disk-shaped InAs quantum dots (QDs) in GaAs on their electronic transport characteristics by employing an empirical tight-binding calculation and a continuum model of the electronic structure. Our model includes both the minibands and the continuum of the host conduction band. The rate of the electron-acoustic-phonon scattering is found using Boltzmann's semiclassical transport theory. The electric conductivity, the Seebeck coefficient and the thermoelectric figure-of-merit for $n$-doped QD arrays are then analyzed as a function of the donor concentration and temperature. For QDs several nanometers in height, the figure-of-merit at temperatures below 100 K as a function of doping is richly structured, reflecting the miniband electron energy spectrum of a QD stack. Certain windows of concentration are revealed, where QD arrays display a geometry-controlled enhanced efficiency as thermoelectric converters. For optimizing the peak values of the figure-of-merit attainable for donor concentrations within the experimentally accessible range, a very thin spacer layer between the QDs $(\ensuremath{\lesssim}5\text{ }\text{nm})$ is found to be most suitable. Assuming that the lattice thermal conductivity can be reduced below $0.5\text{ }\text{W}/(\text{m}\phantom{\rule{0.2em}{0ex}}\text{K})$, a figure-of-merit larger than 2 appears within reach.