A Theoretical Investigation of Enhanced Thermoelectric Figure of Merit of Low-Dimensional Structures

The power factors and electronic thermal conductivities in bismuth telluride (Bi2Te3), lead-telluride (PbTe), and gallium arsenide (GaAs) at room temperature (300K) quantum wires and quantum wells are theoretically investigated. Our formalism rigorously takes into account modification of these power factors and electronic thermal conductivities in free-surface wires and wells due to spatial confinement. From our numerical results, we predict a significant increase of the power factor in quantum wires with diameter w=20 Å. The increase is always stronger in quantum wires than in quantum wells of the corresp onding dimensions. An unconfined phonon distribution assumed based on the bulk lattice thermal conductivity is then employed to evaluate the possible enhancement of the thermoelectric figure of merit. The electronic thermal conductivity of a 20Å diameter wire and a 20Å layer thickness is found to be of no significant decrease. The resultant ZT, calculated for Bi2Te3, PbTe and GaAs, quantum wires and quantum wells, showed increase significantly. The additional thermoelectric figure of merit enhancement is mostly due to the two- and one-dimensional carrier confinement which lead to the enhancement of power factor.