The results of photoluminescence investigations of low-resistivity ZnS:Al crystals, annealed (100h, 1250K) in Bi + BiCl3 melts, were presented. The influence of N-laser radiation annealing (1.5kW, 337.1nm, 10ns) and heating up to 520K on photoluminescence spectra was studied both from the crystal subsurface and from its volume at temperatures ranging from 80 to 520K. Volume and sub-surface spectra were measured from different regions of the cleaved sample surface (normal to two parallel
surfaces contacted with the melt). In the photoluminescence spectra from ZnS volume radiation bands at 426nm related to (ClS) and 496 nm related to (VZn” ClS•) were observed. It was supposed that Zn was diffusing from the crystal volume to the Bi melt, increasing the probability of (VZn” AlZn•)- complex formation. In the sub-surface layer (about 500μm) Bi• (530nm), VS• and their compensating charge states VZn could exist. One could suppose that point defect interaction was based upon the formation of complexes owing to the diffusion process. They also form complexes owing to quasi-chemical reaction. A destruction of the complexes was observed at about 400K. As the temperature increases up to 520K, the intensity of the photoluminescence at the sub-surface sharply decreases. X-ray investigations under high angles have shown the presence of precipitates of Bi2S3 and BiS2 chemical compounds. It was shown that as a result of ZnS:Al:Bi crystal laser illumination and low temperature heating (up to about 520K) in the subsurface layer impurity defect state reorganization and new (Bi2S3; BiS2) phase formation occur, which indicated the possible existence of impurity-defect complexes in the different sites of the host crystal. The main mechanisms of impurity defect state change were center recharging and their motion on dislocations under the conditions close to the fluidity limit of the crystal.

Impurity-Defect States Reorganization in ZnS under the Influence of N2-Laser Radiation. L.I.Bruk, P.I.Ketrush, V.A.Korotkov, R.L.Sobolevskaya, K.D.Sushkevich: Physica Status Solidi B, 2002, 229[1], 343-9