Theory of thermoelectric power factor in quantum well and quantum wire superlattices - art. no. 045324

Calculations are presented for thermoelectric transport in quantum well and quantum wire superlattices, using (i), the full superlattice electronic ba nd structure in (ii) a multisubband inelastic Boltzmann equation for carrie r-phonon scattering. The transport direction is taken to be in the quantum well planes and along quantum wires. It is demonstrated that these two feat ures are needed to give a quantitative treatment of the power factor P in s uperlattice systems. Results are given for PbTe and for GaAs quantum well a nd quantum wire superlattices, including the dependence of P on growth dire ction and on potential offset. For both quantum well and quantum wire super lattices, the dependence of P on potential offset V-o is found to be qualit atively weaker than in previous work based on the constant relaxation time approximation for carrier scattering. These weaker dependences on V-o are t raced mainly to the enhancement of the electron-phonon scattering rates upo n confinement. These results give a different picture of the effects of con finement on P suggesting, for example, that increased confinement in superl attices does not lead to significantly higher P and that free-standing stru ctures, such as free-standing quantum wires, may be particularly attractive for thermoelectric applications.