THERMOELECTRIC FIGURE OF MERIT OF COMPOSITE SUPERLATTICE SYSTEMS

The thermoelectric properties of systems in the form of superlattices have been studied. First, the electrical and thermal conductivities, the thermopowers, and the figures of merit of superlattice structures are given in terms of the bulk parameters of the two constituent materials for conduction both parallel and perpendicular to the superlattice axis. Second, systems in which the layers of one of the materials become sufficiently thin that their electronic properties become effectively those of a two-dimensional quantum well are considered. Numerical calculations are given for such systems with Bi2Te3 quantum wells separated by barriers having the parameters of bulk Pb0.75Sn0.25Te. It is shown that heat and electronic conduction through the barriers has a pronounced effect on the thermoelectric properties of the superlattice and that the figure of merit is decreased substantially for finite barrier thicknesses. © 1995 The American Physical Society.