RAMAN-SCATTERING SPECTRA OF INDIUM-DOPED PBTE

The non-polarized Raman scattering spectra of indium-doped PbTe single crystals were measured in the temperature range between 10 and 300 K. Well resolved peaks at about 68, 126 and 143 cm(-1) were observed for all temperatures. An additional mode appears at about 115 cm(-1) for temperatures below 100 K. The intensity of this mode increases sharply when the temperature is lowered below 25 K, the temperature where a p ersistent photoconductivity effect in PbTe(In) appears. This mode is a ssigned as a local In impurity mode and represents a population of met astable states due to the transfer of electrons from two-electron to o ne-electron metastable impurity states.