Аннотация:The intrinsic nanoscale point defects generating in the crystal lattice of ZnSe during the crystal growth and doping processes strongly determine the functional properties of the material as well as dopant (Fe) solubility. Nonstoichiometry and IR luminescence spectra of ZnSe:Fe powdered preparations and CVD-grown ZnSe:Fe crystals treated by high-temperature gas-static pressing (HIP) were changing depending on Fe doping level and preparation conditions. Whereas the nominally pure CVD-ZnSe crystals had excess of Zn over stoichiometric composition, all the Fe-doped ZnSe crystals had an excess of chalcogen. This correlates with the results of the Zn-Se-Fe phase diagram analysis. Isothermal sections of T-x-y diagrams of ternary Zn-Se-Fe were reconstructed and experimentally confirmed by X-ray diffraction and Energy Dispersive X-ray spectroscopy (EDS) in the temperature range of 873 K - 1088 K. In case of ZnSe:Fe phase with the Fe-concentration level about 1019 cm-3 we observed the shift of the homogeneity range to Se-riched region with the nonstoichiometry level ranging from 5×1017 to 1×1019 cm-3. As a result of the control the intrinsic point defects and Fe-dopant level we achieved the large quantities of differential efficiency of the produced ZnSe:Fe2+ laser as ηslope = 55%.