DOPING EFFECT OF TIN IN Pb1 - xSe AND Pb1 - yS SOLID SOLUTIONS.

The dependence of the carrier density on the tin concentration is determined for Pb//1// minus //xSe (x equals 0-0. 35) and Pb//1// minus //yS (y equals 0-0. 05) solid solutions containing 1 mol. % NaSe or NaS. Changes in the transport properties of holes are observed. In the case of the Pb//0//. //9//5Sn//0//. //0//5S//s//o//l//i//d solid solution the carrier density is several orders of magnitude less than in PbS and it amounts to approximately 10**1**4 cm** minus **3 at T approximately equals 77 degree K. In the presence of anions with a partly filled valence shell some of the tin atoms are transferred to a state with a higher valence and become electrically active impurities (donors), giving rise to localized electron states whose energy positions depended strongly on temperature. An increase in the Sn concentration broadens these impurity states into an impurity band and shifts them relative to the band gap, depending on the composition and external conditions.