Thermal cycling-induced changes in the electrical transport properties of (111) epitaxial, n -type PbTe films

Weak-field magnetoresistance measurements at 297 K were used in conjunction with an appropriate band structure model to detect the substrate-induced strain in n-type PbTe epitaxial films grown on BaF2. Evidence of strain in as-grown films was found. The temperature of the sample was repeatedly cycled from 297 to 4.2 K and back, and the 297-K strain was found to decrease. At the same time, Hall effect and resistivity measurements show that the 4.2-K mobility dropped and the 297- and 4.2-K carrier concentrations increased. The observed effects are ascribed to an extended defect density which grows larger as the number of thermal cycles increases.