Influence Of Ti Related Centers On ZnSe Radiation Spectra

ZnSe annealed in (Zn + 46 wt.% Tl) vapors and in Zn melt with 5 wt.% Tl addition was investigated. The radiation spectra in the regimes of stationary and pulsed photoluminescence (PL) with the time delaying at 77 K were studied. By using colored cathodoluminescence (CCL) combined with the crystal cleavage image in the secondary electrons reflection the impurities and defects volume distribution was evaluated. It was revealed that at the annealing of ZnSe crystals in Tl vapors, the cleavage surface has light blue radiation on the red background with an homogeneous field distribution with the dimensions {approximately} 1.10 {micro}m. On the edge of the cleavage on the depth of 10 {micro}m the region of yellow radiation is observed. At the annealing in the melt the irradiation became blue on a weak red background, the homogeneity enhances. At the room temperature PL spectra correspond with images of cleavage in CCL. In the PL (at 77 K) spectra in the excitation region there were observed: bands at 445 nm (blue radiation); edge radiation at 460 nm, 485 nm with the LO phonons replica (blue region) and in the impurity region: bands 500--570 nm (yellow-green radiation); 600--700 nm and 720--800 nm (redmore » radiation). The investigation of PL of the annealed samples surface allowed the suppose, that the bands at 2.76eV (450 nm), are stipulated by the free-bound transition on the acceptor center (E + 40 meV), including Tl. The comparison of ion and tetrahedronical covalent radiuses of Zn, Se and Tl, electronegativity, probability of Zn{sub i} and V{sub Se} formation at the annealing allowed to suppose that, Tl fills V{sub Se} and forms (Zn{sub i} Tl{sub Se}) and (V{sub Se} Tl{sub Se}) complexes. The carried out theoretical calculations according to the model of two-atom molecule gives the energy of complexes occurrence (E{sub v} + 0.04) eV and (E{sub V} + 0.8) eV. The first value accordingly is in good agreement with the experimental data.« less