The microstructures of p-type (Bi,Sb)2Te3 and n-type Bi2(Te,Se)3 Peltier devices were investigated by using scanning electron microscopy, energy-dispersive X-ray spectroscopy, electron probe micro-analysis and transmission electron microscopy. The substitution of Sb for Bi in p-type material varied around 1at% (3 x 1020/cm3) at the μm-scale. The same behaviour was found for Se and Te in n-type material. These results ruled out Bi and Sb and Se and Te from being statistically distributed in the crystal structure. No evidence for the presence of antisite defects was found by means of electron probe micro-analysis. The materials were highly textured and contained high dislocation densities (109/cm2). Straight dislocations, loops and half-loops that were 10nm in size were observed in the bulk. Elongated mobile dislocations moved in the basal plane, under the electron beam, via successive hops from pinning sites. The lattice defects were expected to affect mainly the low-temperature electronic transport properties, and the lattice heat conductivity. Characteristic defect structures were identified, at the metal/Bi2Te3 interface, which extended into the Bi2Te3 by between 2 and 20μm.

Chemical Composition and Crystal Lattice Defects of Bi2Te3 Peltier Device Structures. D.Eyidi, D.Maier, O.Eibl, M.Westphal: Physica Status Solidi A, 2001, 187[2], 585-600