EFFECT OF SUPERSTOICHIOMETRIC COMPONENTS ON THE SPECTRAL AND KINETIC CHARACTERISTICS OF THE LUMINESCENCE OF ZNSE CRYSTALS WITH ISOVALENT IMPURITIES

The spectral and kinetic parameters of the X-ray luminescence of ZnSe crystals doped with Zn, Se, and Te were investigated during the growth process at temperatures in the range 80-500 K, and also after anneali ng in Zn vapor. ZnSe crystals grown from a stoichiometric mixture, or mixture containing chalcogenide impurities, typically produce the mini mum level of afterglow and a rapid rise of X-ray luminescence, as well as a shift of its peak from the infrared region toward shorter wavele ngths after annealing in zinc. ZnSe crystals grown from material with excess of Zn have a relatively low X-ray luminescence yield and a subs tantial level of afterglow. It is assumed that the growth of Te-activa ted crystals is accompanied by the development of thermally stable com plexes of the form VZnTeSe that act as radiative recombination centers . The introduction of excess Zn into the initial mixture produces a re duction in the concentration of V-Zn and, hence, in the concentration of radiative recombination centers. It is shown that, for free-electro n concentrations n<10(18) cm(-3), the afterglow time constant tau can be described as a function of n by a model of radiative recombination that involves a single impurity level, whereas for n>10(18) cm(-3), th e time constant decreases with increasing n, which cannot be explained in terms of the simple model. It is suggested that radiative recombin ation centers of a new type are produced as a result of prolonged anne aling in Zn vapor. (C) 1997 American Institute of Physics. [S1063-7826 (97)01610-4].