Purification of ZnSe crystals from electrically active background impurities by ytterbium doping

Hall coefficient, electrical conductivity, and electron mobility are investigated for n-ZnSe:Yb single crystals with high concentration of electrically active background impurities ((N-D - N-A) > 1.4 x 10(17) cm(-3)) in the temperature range from 4.2 to 300 K. It is found that increasing concentration of Yb impurity in Zn + Yb melt from 0.03 to 4.00 at.% decreases the concentration of shallow N-D and deep N-Deep donors, as well as the concentration of compensating acceptors N-A by nearly 2 orders of magnitude. A quantitative manifestation of purification of the ZnSe:Yb samples from non-controlled background electrically active impurities and influence of this effect on changes in impurity band parameters and the temperature of electron gas degeneracy are shown. The most probable mechanism of the sample purification due to the formation of electrically neutral complexes based on ytterbium ions and background impurities of donor and acceptor types is discussed. (C) 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim