Abstract
The transport properties of Bi2 – y Sn y Te3 – x Se x solid solutions are studied. The results demonstrate that doping with Sn has a strong effect on the temperature dependences of the thermoelectric power and electrical conductivity of the crystals. This suggests that the valence band of the crystals contains Sn-related resonance states. The point defects and dislocation system in Bi2Te3 and Bi2 – y Sn y Te3 – x Se x solid solutions are studied by transmission electron microscopy. It is shown that the predominant defects in the crystals studied, grown by the Czochralski technique, are dislocations lying in the (0001) plane. The estimated dislocation density is 108 to 109 cm–2, and the primary slip plane is (0001). Electron-microscopic examination indicates the presence of stacking faults and very small dislocation loops in both Bi2Te3 and Bi2 – y Sn y Te3 – x Se x single crystals. Since all of the crystals are highly degenerate semiconductors, it is reasonable to assume that structural defects have an insignificant effect on their electrical properties.
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