Synthesis of lead telluride crystals doped with indium and thulium impurities

S.G. Dorofeev, V.N. Volodin, A.V. Tyurin, V.P. Zlomanov, O.I. Tananaeva

Forth International Conference on Materials Science and Material properties for Infrared Optoelectronics (Kiyv, Ukraine, 1998), p. 159.

Doping of IV-VI semiconductor compounds by elements of the third group results in a complex of interesting phenomena, the nature of which is not finally determined. PbTe crystals were doped by In$_2$Te$_3$ and Tm$_2$Te$_3$ during the growth of crystals from the melt. Monotellurides were not used due to nonquasibinary character of the PbTe-TmTe section of the Pb-Tm-Te phase diagram. The crystals were grown by Bridgman method at a growth rate of (2-4)*10^{-2}$ cm/hour and cooled at a rate of 10$^\circ$/hour. Distribution of doping components, concentration of charge carriers and dislocation density along the crystals were studied. Concentration of indium and thulium in crystals were measured by x-ray method using the calibration curves experimentally obtained for the PbTe--In$_2$Te$_3$ and PbTe-Tm$_2$Te$_3$ sections of solid solutions. The accuracy of the lattice parameter determination were better than 0.002 A, which corresponded to the error in composition less than 0.5~mol.%. The electron concentration in crystals was determined from the Hall measurements, the real structure was studied by selective etching method. The distribution of indium and thulium along the crystals had regions with constant concentration. For PbTe(In) these distributions were compared with those calculated for various models. The best agreement was found for the Pfann model. The dependence of electron concentration and dislocation density along the crystals had nonmonotone character. Possible explanations of this phenomena is discussed. The work was supported by RFBR grant N 96-03-32932.

Laboratory of Physics and Chemistry of Semiconductors