We present a parametric analysis of the thermoelectric power factor of single-carrier semiconductors for nanowires, thin films, and bulk. We consistently find a reduction in the peak power factor in many-subband nanostructures compared to bulk, independent of the specific materials parameters, system geometry, or dimensionality. A universal relation between the optimal power factor and the system size, common to all single-carrier materials, is developed for nanowires and thin films. The common nonmonotonic trend highlights the competing effects of quantization and degeneracy on the transport properties of semiconductor nanostructures. The model predicts decreases of up to 28$\%$ and 22$\%$ in the peak power factor in nanowires and thin films, respectively, relative to the bulk value. This study provides insights to successful figure-of-merit enhancement strategies.

• Received 2 June 2011

DOI:https://doi.org/10.1103/PhysRevB.84.205410