Defects in Bi2Te3-xSex single crystals

Single crystals of a ternary system based on Bi2Te3-xSex (nominally x = 0.0-0.2) were prepared using the Bridgman technique. Samples with varying content of Se were characterized by the measurement of lattice parameters, electrical conductivity sigma(perpendicular to c) and Hall coefficient R-H(B parallel to c). The actual concentration of selenium c(Se) in the samples was determined using atomic emission spectroscopy. While a small selenium concentration enhances the free hole concentration P after passing a maximum, the hole concentration decreases at higher selenium concentrations. The extreme-like dependence P = f(c(Se)) is explained in terms of a change of the native defect concentration due to the substitution of selenium atoms by tellurium ones.