Investigation of effective mass of carriers in Bi2Te3Sb2Te3 superlattices via electronic structure studies on its component crystals

The electronic structures of Bi2Te3 and Sb2Te3 were computed and related to the thermoelectric properties of Bi2Te3̸Sb2Te3 superlattices. The authors found that the similarity of the electronic structure of the two materials permits the Bi2Te3̸Sb2Te3 superlattices inherit high band edge degeneracy, and thus have high electrical conductivity. From the calculated effective mass along the superlattice growth direction, we infer that presence of more Sb2Te3 than Bi2Te3 in the superlattice leads to a smaller effective mass and enhanced carrier mobility. Furthermore, our results suggest that external tensile strain parallel to the interface may further improve the thermoelectric performance of the Bi2Te3̸Sb2Te3 superlattices.