Photoluminescence Spectra of ZnS:Al Crystals Annealed in a Melt with Bismuth and Chlorine Ions

The results of the temperature investigations (77–520 K) of the photoluminescence (PhL) of lowohmage ZnS monocrystals annealed in bismuthbased melts are presented. It is shown that the ion composition of the annealing medium produces a determining effect on the formation of an impuritydefect composition of the radiative centers. The dominant contribution to the PhL radiation is attributed to the centers based on the vacancies of sulfur and zinc and aluminum and chlorine. In the nearsurface region and in the bulk of the crystal, the PhL spectra differ. The PhL spectra in the nearsurface region of the crystal are determined by the complex bismuth centers and correspond to the characteristic features of the intracenter transitions. We propose two possible models of radiative centers: (V_Zn ^/Bi_Zn )^times and DX centers. It has been found that the simultaneous action of the radiation from a pulsed nitrogen laser and the heating at a temperature from 410 to 518 K destroy the radiative bismuth centers and lead to the formation of precipitates Bi₂S₃ and BiS₂.