Use of similatity criteria for evaluating the thermoelectric figure of merit of superlattices

Abstract: In this paper, general relationships that allow evaluating the figure of merit of both two-dimensional superlattices and three-dimensional crystals with a quadratic and isotropic energy spectrum of free charge carriers are derived. It is shown that with the same values of the so-called dimensionless temperature and scattering coefficient, the figure of merit of superlattices is always lower than that of three-dimensional crystals. The figure of merit of superlattices can become higher that that of three-dimensional crystals if the dimensionless temperature of free charge carrier gas and (or) scattering coefficient in them is considerably higher than in three-dimensional crystals.