Optical reflection in Pb0.78Sn0.22Te doped to 3 at. % with indium

The spectral dependence of the optical reflection of n-(Pb0.78Sn0.22)1−xInxTe (x=0.02 and 0.03) and p-Pb0.78Sn0.22Te doped with 3 at. % In and 1.5 at. % Tl has been investigated at T=300 K. Minima associated with plasma vibrations of the free carriers were observed in all the experimental spectra. The electron density n and the hole density p were estimated by the Kukharskii-Subashiev method. It is shown that the value of n so obtained is much smaller than its value obtained from the Hall effect only in n-(Pb0.78Sn0.22)0.97In0.03Te in which, as had been assumed previously, hopping conductivity dominates. This result may be viewed as an independent experimental confirmation of the unusual character of conduction in n-(Pb0.78Sn0.22)1−xInxTe solid solutions with high indium content.