Electrical and magnetic investigations were made of Yb-doped crystals. It was found that additional shallow donors and paramagnetic centers were not introduced into the doping process, that the hole conductivity of doped crystals was controlled by A-centers, and that their ionization energy depended upon the Yb impurity concentration. It was proposed that the Yb atoms deformed the lattice so that the components of the complex A-center moved away from each other when the concentration increased.

E.S.Nikonyuk, V.Z.Shlyakhovuy, M.O.Kovalets, M.I.Kuchma, Z.I.Zakharuk, V.M.Frasuniak: Journal of Crystal Growth, 1996, 161, 186-9