Band crossing evidence in PbSnTe observed by optical transmission measurements

Using high quality epitaxial layers, we have obtained direct evidence of th e band inversion in the Pb1-xSnxTe system. The samples, covering the whole composition range, were grown by molecular beam epitaxy on (111)BaF2 substr ates. A minimum in the resistivity as a function of temperature was observe d for all samples with Sn composition 0.35 less than or equal to x less tha n or equal to 0.70. In the same samples and at the same temperature, temper ature dependent optical transmission measurements have revealed a change in signal of the energy gap temperature derivative, a direct evidence of the hand inversion. However, the temperature for which the inversion occurs is not the one expected by the band inversion model. This discrepancy is suppo sed to be due to the Burstein-Moss shift caused by the relatively high hole concentration observed in these samples.