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Hall coefficient and resistivity measurements have been made on 29 single crystals (mostly synthetic) of PbS, PbSe, and PbTe between room temperature and 4.2'K. Almost all of the samples had extrinsic carrier concentrations of the order of 10' per cm', as deduced from the Hall coefficients which were essentially constant over the entire temperature range investigated. Hall mobilities were calculated from the Hall and resistivity data, and were found to increase rapidly with decreasing temperature.Between room temperature and about 50'K the mobility behavior was essentially intrinsic and varied approximately as T~2.Below 50'K the mobility curves turned gradually toward the horizontal in a manner resembling the residual resistance phenomenon observed in metals. Values as high as 800000 cm'/v-sec were attained at 4. 2'K despite the large carrier concentrations present in all the samples. A simple experiment was performed which suggests that dislocations are the principal scattering mechanism below 50'K, rather than the charged point defects associated with the extrinsic carriers. The possibility that a high static dielectric constant could explain the large mobilities at low temperatures is discussed.

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The magnetic field dependence of the Hall coefficient at 296° and 77°K, and the temperature dependence of the weak-field Hall coefficient and the resistivity between 296° and 77°K were studied in single-crystal samples of p-type PbTe having carrier concentrations ranging from 4.9×1017 to 1.7×1019 per cm3. The Hall data at 77°K are quantitatively consistent with magnetoresistance data which have previously established the presence of 〈111〉 ellipsoids in the valence band. They are not consistent with a low-temperature two-band model, proposed by Stiles from de Haas-van Alphen data at 4.2°K, unless the band edges lie at approximately the same energy (as Stiles found) and unless the carrier mobilities in the two bands are nearly alike. On the other hand, both the Hall and resistivity data above about 150°K do exhibit two-carrier effects suggesting the presence of a lower mobility band at an energy about 0.1 ev below those bands which are occupied at low temperatures.

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