The Effect of Thermally Produced Lattice Defects on the Electrical Properties of Tellurium

概要

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The electrical properties of tellurium crystals are re-investigated under the assumption of excess holes in the valence band owing to the trapping of electrons by the lattice defects generated by the thermal excitation of lattice atoms. From the observed data of the electrical conductivity and the Hall effect, and by applying the treatment of composite semiconductor in which the extrinsic acceptors and the thermally produced acceptors both generate holes other than the intrinsic pair excitations of electrons and holes, the width of the forbidden energy band 〓E, the effective masses of electrons and holes m_e and m_h, and the carrier mobilities due to the lattice scattering μ_eL and μ_hL are determined as 〓E = 0.32+1.9×10^<-4>TeV, m_e = 0.68m, m_h=0.91m and μ_eL = 2.1μ_hL = 6.1 × 10^6T<-3/2>cm^2/volt・sec. The sign reversals of Hall effect and thermoelectric power from minus at lower temperatures to plus at higher ones found in the pure intrinsic region are explained by the predominance of holes released from the lattice defects the concentration of which increases with the rise of temperature, and the optimum fit of the calculated characteristics to the observed one is obtained by assuming the activation energy to produce one lattice defect as 0.52 eV.
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