The concentrations of impurities and point defects in melt grown ZnSe Sergiy Galkin   Institute for Scintillation Materials of NAS of Ukraine, 60 Lenin ave., Kharkov 61158, Ukraine galkin@isc.kharkov.com

Luminescent parameters of the ZnSe at low temperatures depend on: presence of chemical impurities (especially polyvalent metals). violations of the stoichiometric composition (due to the formation polyselenids). presence of point defects that can act as traps and scattering centers.

Contents of the main impurities in the charge and the grown ZnSe crystal Admixture Charge (mas. %) Krystal Ag < 210-5 Cd < 310-5 Cu < 710-6 910-5 Mg < 110-6 2.710-4 Al < 210-6 2.110-3 Cr < 410-6 710-6 Ca < 310-6 410-3 Mn 4.710-5 Fe 8.510-4 Ni < 610-6 Sn Sb Pb < 510-5 Si 1.310-3 S < 110-4 С 110-3 4.810-2 О 110-4 4.610-2

Optical absorption in the infrared spectrum Distribution of the absorption coefficient along the axis of the ZnSe crystal ZnSe transmission spectra before (1) and after (2) heat treatment in zinc vapor

The concentration of VZn, V’Zn and V∙Se in ZnSe is reduced by the low-temperature heat treatment Zn-Se phase diagram

Defects formation process by ZnSe crystals growing ZnSel → Zng + 1/2Se2 Zn Increase concentration vacancies factors Effects in ZnSe Melt overheating Stoichiometry disbalance Isovalent substitution Local deformation of crystal lattice Donor doping Vacancies generation in conformity with electric neutrality rule Se VZn

Cation doped ZnSe lattice paramethers Entering into the crystal a small amount of a donor impurity ZnSe lattice parameter decreases due to the generation of vacancies

Point defects and ZnSe scintillation parameters Defects complex ZnSe stoichiometry Luminescence, nm VSe ­- OSe- VZn Se excess 970 VZn - Zni – MZn Stoichiometric composition 640 VZn - Zni Zn excess 610 Exciton 460

Conclusions The ZnSe luminescence intensity depends on the: - carbon impurities amount; composition and concentration of point defects. Very important is optimal regime of ZnSe thermal treatment.