Effect of Electron and Phonon Confinement on the Thermoelectric Figure of Merit of Semiconductor Quantum Wires

We have theoretically investigated the effect of different boundary conditions on the electron and phonon transport in quantum wires. Three possible cases corresponding to electron, phonon and combined electron-phonon confinement have been considered. The numerical calculation of the transport coefficients as functions of the wire radius has been carried out for a silicon quantum wire. Based on the results of simulation, we have predicted a possibility of significant enhancement of the thermoelectric figure of merit. The maximum enhancement can be achieved by combining electron and phonon confinements. The effect becomes stronger as the wire radius decreases. The main contribution to the predicted enhancement comes from the drop in the lattice thermal conductivity caused by the spatial confinement of acoustic phonons.