Low carrier concentration crystals of the topological insulator   Bi$_2$Te$_2$Se
  We report the characterization of Bi$_2$Te$_2$Se 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 ($> 1 \mathrm{\Omega cm}$) and low carrier concentration ($\sim 5\times 10^{16}$/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. 
Shuang Jia, Huiwen Ji, E. Climent-Pascual, M. K. Fuccillo, M. E.   Charles, Jun Xiong, N. P. Ong and R. J. Cava
cond-mat.str-el