Two charge states of Gd-impurities in the PbTe:Gd crystals

Study of the Gd Impurity Influence on the Defect Structure of Pb1-xSnxTe Crystals by Means of119Sn M�ssbauer Spectroscopy

“…Data presented in [10] give rise to the same conclusion. Thus, the observed 119 Sn Mö ssbauer spectrum line broadening could be caused by the influence either of the Gd impurity or the main donor centers --Te vacancies, that determine the n-type conductivity of the investigated crystals doped with Gd [13].…”

“…Therefore, it is singly charged relative to the main state of the ions of the metal sublattice, which are substituted by Gd in the crystal [13]. The Te vacancy, which is the main source of free electrons in the materials under the investigation, exists in the doublecharged donor state with zero energy of ionization [15].…”

Pecularities of EPR spectra of the Gd impurity in the Sn-Rich Pb1−x Sn x Te(Gd) solid solutions

“…In the present work, we study the behavior of the Gd impurity ions in the crystals of Pbl_xSnxTe solid solution, asa follow-up of the systematic investigations of the influence of this dopant on the physical properties of the IV-VI semiconductors [4][5][6][7][8]. Behavior of the Gd impurity in the investigated materials is nontrivial in many aspects, e.g., it enables one to control efficiently the structural, optical, and electrophysical parameters of lead and tin tellurides.…”

“…Thus, doping with Gd leads to a decrease in the hole concentration in the Pb~_xSn~Te in the whole range of composition x from 0 up to 1. It may also cause a crystal conductivity inversion from the hole (p) type to the electron (n) type at certain values of the Gd impurity concentration NGd and matrix composition x [3][4][5][6].…”

“…The ability of gadolinium to actas a donor in the investigated materials may be explained in two different ways: (1) by electrical activity of the Gd impurity itself [3,9] or (2) by its indirect action through the change of the dominant point defects at the crystallization point, i.e., the presence of Gd favors the vacancies in the chalcogen sublattice [5][6][7], which constitute the doubly charged donors with zero activation energy [I0]. The first mechanism of the Gd donor action should involve the presence of the donor impurity centers in the Gd 3+ charge state in the concentrations not lower than that for the free electrons in doped crystals, which is, however, not observed experimentally [7].…”