Luminescence properties of ZnSe single crystals co-doped with Fe and Cr

The luminescence properties of two co-doped ZnSe:(Cr, Fe) single crystals, grown by the Bridgman method, have been studied using photoluminescence techniques. Structural characterization by high-resolution X-ray diffraction (HR-XRD), electron paramagnetic resonance (EPR) and scanning electron microscopy (SEM) has revealed that the samples differ in terms of dopant concentration and intrinsic native defects. Analysis of the VIS and near-IR photoluminescence spectra, based on the modified crystal field theory and DFT calculations has shown that Fe and Cr exist in two charge states (+2/+3) and can be located in both tetrahedral and octahedral positions. In the blue light region, quantum dots (QDs) appear. These represent clusters of three Cr-containing octahedral complexes accompanied by Zn vacancies, anticipating the formation of spinel ZnCr₂Se₄ inclusions in the host chalcogenide ZnSe matrix.