Optical absorption and chromium diffusion in ZnSe single crystals

ZnSe:Cr single crystals were obtained using diffusion-related doping with chromium. The diffusion of chromium was performed in an atmosphere of saturated zinc vapors, and the metallic Cr layer deposited on the crystal surface was used as the source. Lines corresponding to chromium absorption at 2.766, 2.717, and 2.406 eV were observed in the optical-density spectrum at 77 K. The highest chromium concentration in the crystals was determined from infrared absorptance in the region of 0.72 eV and was found to be equal to 8 × 10¹⁹ cm^?3. It is shown that the diffusion profile of the chromium impurity can be determined by measuring the optical density of the crystals in the visible region of the spectrum. The diffusion coefficients D of chromium in ZnSe crystals at temperatures of 1073–1273 K are calculated. An analysis of the temperature dependence D(T) made it possible to determine the coefficients in the Arrhenius equation: D₀ = 4.7 × 10¹⁰ cm²/s and E = 4.45 eV.