Effect of the Energy Dependence of the Carrier Scattering Time on the Thermoelectric Power Factor of Quantum Wells and Nanowires

Appl. Phys. Lett. 100, 242106 (2012)https://ireap.umd.edu/10.1063/1.47293812012Journal ArticleAdvanced Materials and Nanotechnology

The size-dependence of the thermoelectric power factor of thin-films and nanowires is theoretically investigated from the electric quantum limit (EQL) to the bulk-like regime. Different functional forms of the energy-dependent relaxation time τ(E) are incorporated in the model to account for carrier scattering mechanisms typical in semiconductor nanostructures. The calculations show that the steeper the increase in the relaxation time with carrier energy, the higher the power factor-to-average scattering time ratio, PF / <τ>, confirming the benefits of the preferential scattering of low-energy carriers to thermoelectric performance. However, outside the EQL, the power factor values are lower in the low-dimensional structures than in their three-dimensional counterparts. Thus, the power factor is more readily improved by modifications of the scattering rates than by quantization of the energy states.