Seebeck Effect in IV–VI Semiconductor Films and Quantum Wells

Theoretical calculations of the Seebeck coefficients of IV–VI semiconductors and quantum wells were performed, taking into account temperature-dependent band gaps, nonparabolicity, and anisotropy of effective masses in the framework of the Boltzmann equation. The Seebeck coefficient depends on both the density of states and a kinetic term determined from the balance between drift and diffusion currents. The theoretical Seebeck coefficients of PbTe and PbSe films were compared with experimental values, and excellent agreement was obtained. In lead-salt IV–VI materials with a positive temperature dependence of the band gap, the kinetic part becomes small or has a negative effect on the Seebeck coefficient. Strong enhancement of the Seebeck coefficient is expected theoretically in n-type PbTe/PbSe superlattices, resulting from the increase of the kinetic part due to the effective-mass difference between PbTe and PbSe.