Enhanced thermoelectric performance in PbTe-based superlattice structures from reduction of lattice thermal conductivity

We have fabricated two-dimensional $n$ -type $\mathrm{Pb}\mathrm{Te}∕\mathrm{Pb}{\mathrm{Te}}_{0.75}{\mathrm{Se}}_{0.25}$ structures using an evaporation process. In optimized films exhibiting a high-quality superlattice structure, a significant reduction in lattice thermal conductivity has been experimentally measured. The reduction would indicate enhanced thermoelectric device performance compared to standard PbTeSe alloys given that the electrical components, specifically, the Seebeck coefficient and electrical resistivity, were not observed to deteriorate from bulk values. The analysis of these films shows continuous layers with a true two-dimensional superlattice structure, as opposed to the $\mathrm{Pb}\mathrm{Te}∕\mathrm{Pb}\mathrm{Se}$ system that exhibits zero-dimensional structures from self-assembly. The room-temperature measurement of cross-plane figure-of-merit in a $n$ -type $\mathrm{Pb}\mathrm{Te}∕\mathrm{Pb}{\mathrm{Te}}_{0.75}{\mathrm{Se}}_{0.25}$ device structure by the transient method has been combined with temperature-dependent measurements of in-plane resistivity and Seebeck coefficient to yield evidence of enhanced thermoelectric performance. The similarities and differences between the superlattice in the $\mathrm{Pb}\mathrm{Te}∕\mathrm{Pb}{\mathrm{Te}}_{0.75}{\mathrm{Se}}_{0.25}$ system and the ${\mathrm{Bi}}_2{\mathrm{Te}}_3∕{\mathrm{Sb}}_2{\mathrm{Te}}_3$ material system are presented.