On the density-of-states effective mass and charge-carrier mobility in heteroepitaxial films of bismuth telluride and [Bi.sub.0.5][Sb.sub.1.5][Te.sub.3] solid solution

It is shown that the Seebeck coefficient [alpha], the power factor [[alpha].sup.2][sigma], and the density-of-states effective mass m/[m.sub.0] in heteroepitaxial films of [Bi.sub.0.5][Sb.sub.1.5][Te.sub.3] 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 [alpha], [[alpha].sup.2][sigma], and m/[m.sub.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.