On the density-of-states effective mass and charge-carrier mobility in heteroepitaxial films of bismuth telluride and Bi0.5Sb1.5Te3 solid solution

It is shown that the Seebeck coefficient α, the power factor α2σ, and the density-of-states effective mass m/m 0 in heteroepitaxial films of Bi0.5Sb1.5Te3 solid solution are higher than the corresponding characteristics of bulk thermoelectric materials. The elevated values and weak temperature dependences of these parameters lead to a rise in the parameter proportional to the effective mass, the charge-carrier mobility, and the figure of merit. The character of change in α, α2σ, and m/m 0 is determined by the peculiarities of the mechanism of charge-carrier scattering, the anisotropy of the constant-energy surface, and the possible influence of topological surface states of Dirac fermions in the films.