I–Vmeasurements and temperature dependence of electrical conductivity on polycrystalline
samples of Bi2Se3 and SnBi4Se7 have been performed. From the analysis of the temperature
dependence of electron concentration in the activation regime above room temperature, the effective
massm e* has been determined. Some intrinsic and contact properties such as barrier heights, ideality
factors, and carrier concentrations have been investigated by usingI–Vcharacteristics. It has been
found that all samples exhibit Ohmic and space charge limited conduction at low and high fields