Yatsun V. Optical and electrophysical properties of zinc selenide single crystals doped with iron and nickel

The thesis is devoted to the influence of impurities of iron and nickel on the absorption, luminescence and photoconductivity of zinc selenide crystals, determination of the scheme of optical transitions, as well as diffusion parameters of these impurities in single crystals of ZnSe. It was first detected and identified a series of absorption lines of ZnSe:Fe (2.46, 2.41, 2.30, 2.22, 2.17, 2.09, 2.03, 1.95, 1.88, 1.77 eV) and ZnSe:Ni (2.57, 2.34, 2.14, 2.02, 1.86 eV) in the visible region of spectrum. It also shown that the ZnSe:Fe and ZnSe:Ni crystals have photoluminescence in the visible spectrum. A series of emission lines of ZnSe:Fe crystal (2.44, 2.38, 2.33, 2.28, 2.20, 2.14, 2.04, 1.97, 1.89, 1.82, 1.74 eV) and ZnSe:Ni (2.24, 2.05, 1.97, 1.82 and 1.74 eV) was discovered. The founded lines in absorption and emission spectra are identified as due to intracenteral transitions within the doubly charged iron and nickel impurity ions, respectively. The correspondence of the calculated diffusion impurity profiles of iron and nickel, and experimentally determined profiles of the relative optical density of the doped crystals are established. The diffusion parameters of the investigated impurities in the ZnSe crystals are calculated. The high-temperature impurity photoconductivity in ZnSe:Fe and ZnSe:Ni crystals are founded. It is shown, that impurity photoconductivity is due to optical transitions of electrons from the ground states of Fe2+ and Ni2+ ions to the levels of their excited states, followed by thermal emission of electrons into the conduction band.