Far-infrared study of impurity local modes in gallium-doped PbTe

We present far-infrared reflection spectra and results of galvanomagnetic m easurements of PbTe single crystals doped with gallium between 10 and 300 K . The analysis of the far-infrared reflection spectra was made by a fitting procedure based on the model of coupled oscillators. Together with the str ong plasmon-phonon coupling we obtain three local modes of gallium at about 122, 166 and 192 cm(-1). The position of these modes depends of impurity c enter charge, and their intensity depends of temperature and of gallium con centration. Persistent photoconductivity effect was registered in the sampl e with 0.4 at.% Ga by galvanomagnetic and far-infrared measurements. (C) 19 99 Elsevier Science B.V. All rights reserved.