Thermopower of superlattices as a probe of the density of states distribution

Abstract

It is shown that the low-temperature thermopower S of a superlattice as a function of dopant concentration provides direct information about the one-electron density of states of the superlattice and the location and width of the minibands. The thermopower is predicted to be anisotropic according to whether the temperature gradient is along or perpendicular to the superlattice axis. In the former case it vanishes for the Fermi level outside the minibands, depending on the scattering mechanisms operative, but does not vanish there in the latter case. Finally, a sign reversal in S indicative of hole-like behaviour is predicted for energies near the top of the minibands.