Anomalous transport properties of a new compositionally modulated semiconductor-semimetal system: PbTe-Bi

Compositionally modulated structures (CMS) of PbTe—Bi with wavelengths between 38–140 A were prepared by thermal evaporation on muscovite mica substrates. There was a well defined epitaxy with the (111) plane and the [110] axis of the CMS parallel to (001) and [100] of the mica. The dc resistivity, Hall coefficient, and magnetoresistance were measured in the temperature range of 1.8 to 300 K and for magnetic fields up to 50 kG. All samples displayed an anomalous logarithmic increase in the resistance at low temperature. The magnetoresistance increased logarithmically with magnetic field H in large fields for the samples with thick PbTe layers (> 45 Å), while it went as H^1/2 for the samples with thin PbTe layers (> 30 Å). The sign of the Hall coefficient changed from negative to positive with increasing Bi layer thickness and the positive Hall coefficient could be changed in sign by increasing the PbTe layer thickness.