Electric-field-effect thermoelectrics

A significantly large thermoelectric "figure of merit" in a bipolar semicon ductor is achieved by converting it, by doping, into an essentially monopol ar semiconductor. We show here, that for a bipolar semiconductor film, havi ng a thickness smaller than the screening length, there is an alternative t o doping to obtain a practically monopolar semiconductor. The electric-fiel d effect (EFE) or the ferroelectric-field effect can be used to quench the concentration of one type of charge carriers. We show that this method is p articularly suited for narrow-gap semiconductors and for semimetals, having sufficiently high dielectric permittivity. We also show that this "EFE dop ing" is free from the drawbacks of conventional doping. Our analysis demons trates that increased values of the figure of merit are feasible. We presen t here the theory and the figure-of-merit calculation for typical cases of the bipolar semiconductor thermoelectric film under EFE doping. Numerical r esults for a film of the PbTe type are presented. (C) 2001 American Institu te of Physics.