CHANGE OF LIGHT HOLES VALENCE-BAND IN LEAD-TIN TELLURIDE FILMS BY ISOVALENT SUBSTITUTION OF CHALCOGEN ATOMS

Rotational weak-field magnetoresistance measurements at 78 K were used to determine the parameters of the valence band of light holes for Pb 0.8Sn0.2Te and Pb0.8Sn0.2Te0.98S0.02 epitaxial films grown on (111)-or iented BaF2. It was shown that an isovalent substitution of 2% of tell urium atoms by sulphur atoms in solid solution films of lead telluride -tin telluride leads to the decrease of the energy splitting value of valence band valleys Delta epsilon(v) from 18 meV to 2 meV. The physic al reasons for this phenomenon were analysed, Obtained experimental da ta were compared with the results of other experiments on photolumines cence and concentration dependencies of thermoEMP coefficient. (C) 199 7 Elsevier Science S.A.