Low-carrier-concentration crystals of the topological insulator Bi2Te2Se

We report the characterization of Bi2Te2Se crystals obtained by the modified Bridgman and Bridgman-Stockbarger crystal-growth techniques. X-ray-diffraction study confirms an ordered Se-Te distribution in the inner and outer chalcogen layers, respectively, with a small amount of mixing. The crystals displaying high resistivity (>1 Omega cm) and low carrier concentration (similar to 5 x 10(16)/cm(3)) at 4 K were found in the central region of the long Bridgman-Stockbarger crystal, which we attribute to very small differences in defect density along the length of the crystal rod. Analysis of the temperature-dependent resistivities and Hall coefficients reveals the possible underlying origins of the donors and acceptors in this phase.