First-principles investigation of the electronic structures and Seebeck coefficients of PbTe/SrTe interfaces

By introducing a suitable barrier, carrier filtering can yield a high Seebeck coefficient by filtering out electrons (or holes) with low energy. To understand carrier filtering in a PbTe/SrTe interface, the first-principles method and semiclassical Boltzmann theory are used to investigate electronic structures and Seebeck coefficients of PbTe/SrTe (110) and (100) interfaces. The PbTe/SrTe heterostructure is found to be a type-I interface that can form an energy barrier that filters low-energy carriers. Such carrier filtering induces a large in-plane Seebeck coefficient of ∼277 μV K−1 (T = 600 K) with a fixed carrier concentration of 1.6 × 1020 cm−3. This large in-plane Seebeck coefficient is attributed to the Te-p states and the strong asymmetry of the transmission. Additionally, the values of the Seebeck coefficient of p-type PbTe/SrTe (110) are larger than those of the n-type one, and the electronic properties of the PbTe/SrTe (100) interface are similar to those of the PbTe/SrTe (110) interface.