In this work, the electrical properties of Pb1−xSnxTe epitaxial layers with Sn composition covering the whole range were investigated. The samples were grown on (111)BaF2 substrates in a molecular beam epitaxy system using PbTe, SnTe, and Te solid sources. As the alloy composition varies from PbTe to SnTe, the hole concentration increases exponentially from 1017 to 1020 cm−3 for Te-rich sources and from 1017 to 1019 cm−3 for stoichiometric ones. The resistivity of the samples, which depends mainly on their hole concentrations, shows an exponential dependence on the temperature with a slope which decreases as x goes from 0 to 1. For all Pb1−xSnxTe samples with x in the range of 0.35–0.7, the resistivity curve shows a very well defined minimum at low temperatures. This anomalous behavior is supposed to be related to the band crossing, where the energy gap temperature coefficient changes sign. The temperatures where the minimum in the resistivity occurs only agree with the ones predicted by the band inversion model around x=0.4, exhibiting a large deviation to lower temperatures as x increases.

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Using high quality epitaxial layers, we h a ve obtained direct evidence of the band inversion in the P b 1,x Sn x T esystem. The samples, covering the whole composition range, were grown by molecular beam epitaxy on 111 BaF 2 substrates. A minimumin the resistivity as a function of temperature was observed for all samples with Sn composition 0:35 x 0:70. In the same samples and at the same temperature, temperature dependent optical transmission measurements have revealed a change in signal of the energy gap temperature derivative, a direct evidence of the band inversion. However, the temperature for which the inversion occurs is not the one expected by the band inversion model. This discrepancy is supposed to be due to the Burstein-Moss shift caused by the relatively high hole concentration observed in these samples.

PbTe/SnTe superlattices were grown on ͑111͒ BaF 2 substrates by molecular beam epitaxy using PbTe as buffer layers. The individual layer thickness and number of repetitions were chosen in order to change the strain profile in the superlattices from completely pseudomorphic to partially relaxed. The superlattices structural properties were investigated by making reciprocal space maps around the asymmetric ͑224͒ Bragg diffraction points and /2⌰ scans for the ͑222͒ diffraction with a high resolution diffractometer in the triple axis configuration. With the strain information obtained from the maps, the ͑222͒ /2⌰ scan was simulated by dynamical diffraction theory. The simulated spectra of the pseudomorphic superlattices, in which the in-plane lattice constant is assumed to be the same as the PbTe buffer throughout the superlattice, fitted in a remarkably good agreement with the measured data, indicating that almost structurally perfect samples were obtained. For the thicker superlattices, the ͑224͒ reciprocal space maps revealed a complex strain profile. Our results show the importance of detailed structural characterization on the interpretation of the electrical properties.