Physica B 308–310 (2001) 1057–1060 Native defects and rare-earth impurities interaction in IV–VI crystals D. Zayachuk a, *, Ye. Polyhach a , E. Slynko b , O. Khandozhko b , V. Kempnyk c , D. Baltrunas d a Lviv Polytechnic National University, Semicond. Electronics Department, 12 vul. Bandery, 290646 Lviv, Ukraine b Institute of Material Science NASU, Chernivtsy, Ukraine c Institute of Materials, Lviv, Ukraine d Institute of Physics, Vilnius, Lithuania Abstract Both EPR spectra of Gd impurity and 119 Sn M . ossbauer spectra in Pb 1x Sn x Te grown from the melt by Bridgman method and doped with Gd impurity during the growth process were investigated. It was ascertained that EPR spectra behavior depended on rare-earth impurity concentration, doping method and matrix composition. It was shown that there were some correlations between Gd EPR spectra behavior and 119 Sn M. ossbauer spectra parameters in doping crystals under investigation. The results obtained are treated on the basis of the model ‘‘Gd impurity–Te-vacancy’’ complexes, whose creation is caused by the interaction between point defects in the matrix and Gd impurity ions during growth process. r 2001 Elsevier Science B.V. All rights reserved. Keywords: EPR; M. ossbauer effect; Native defects; Gadolinium 1. Introduction Investigations of rare-earth element (REE) impurities behavior in semiconductors and their influence on physical properties as well as extension of their practical applications are of great scientific interest at the moment [1–4]. Due to the ‘‘cleaning effect’’ caused by REE and their electronic configuration being different from other impurities as well as the presence of unfilled 4f-electron shells, it could be possible to improve operating parameters of doped semiconducting materials and to create semiconductors with new physical properties for fiber-optics communication and spintronics. This work keeps on methodical investigation of Gd impurity behavior in lead and tin telluride crystals [4–6]. Its main aim is to provide a model of Gd 3+ charge state creation in materials under the investigations suggested in the preceding work [6] with new arguments. Accord- ing to this model Gd 3+ ion exists as a component part of ‘‘Gd impurity–Te-vacancy’’ complex and arises out of interaction with Te vacancy. This conclusion was drawn during the investigations of PbTe:Gd crystal, where Gd was added as a hyperstoichiometric dopant. Present work is an extension of this case, in which Gd was added as a metal component substituting dopant, during the growth from the melt of both Pb 1y Gd y Te and Pb 1xy Sn x Gd y Te solid solutions. It was assumed that if Te vacancy really takes a dominant part in Gd 3+ charge state creation, then it should be indicated in Gd EPR spectra depending on doping method and metal sublattice composition of Pb 1x Sn x Te, because these factors are directly connected with Te vacancies concentration. Obtained investigation results are pre- sented below. 2. Samples and experiments Single crystals of PbTe and its solid solutions with SnTe, grown from the melt by Bridgman method and doped with Gd, during the growth process, have been *Corresponding author. E-mail address: zayachuk@polynet.lviv.ua (D. Zayachuk). 0921-4526/01/$-see front matter r 2001 Elsevier Science B.V. All rights reserved. PII:S0921-4526(01)00839-0