Transport properties of Sn and SbI3 doped single crystal p-Bi 2Te3

Abstract

Bi2Te3-Sb2Te3 solid solutions, the most commonly used room temperature thremoelectrics, are characterized by inhomogeneities and defects of various types, and doping aggravates the situation with crystal homogeneity. However, several publications reported on unusual behaviour of Sn in Bi2Te3, specifically, on improvement of spatial distribution of Seebeck coefficient over a cleavage face. This work reports on measurements done on single crystals of Bi 2Te3 doped with 0.5% Sn as grown by the Czochralski method using a floating crucible. To shift the Fermi level, further doping with the traditional iodine impurity, was introduced as SbI3. X-ray diffraction, ρ⊥(T) (4-point, low freq. A.C.), ρ⊥(4K, 0 < H < 8T ρ C3-axis), and Rhall measurements were carried out. Two different behaviours are observed: metallic-like resistivity vs. temperature and magnetoresistivity vs. magnetic field for 0.05%SbI 3 and non-monotonic resistivity temperature dependence and quantum oscillations in the magnetoresistivity for 0.1%SbI3. The X-ray results and the quantum oscillations indicate the high quality of the single crystals despite the high content of 2 impurities. The observed results are explained by the existence of a band of quasi-local impurity states of Sn located on the background of Bi2Te3 valence band, whose energy levels are estimated. © 2009 IOP Publishing Ltd.