Photoluminescence of ZnSe:Ag single crystals

Photoluminescence (PL) and photoluminescence excitation (PLE) spectra of n-ZnSe single crystals doped with Ag were investigated in the temperature range from 82 to 300 K. It has been established that the high-temperature annealing of the crystals in Zn + Ag melt with small content of Ag enhances intensities of all the bands in the PL spectrum. However, starting with the concentration of 2 at% Ag in Zn melt, the intensity of the donor-bound exciton band (2.788 eV) with Agi as a donor (E-D = 0.025 eV) decreases. This is stipulated by delocalization of impurity electron states and by formation of a donor impurity band. With the increase of Ag concentration in Zn + Ag melt, the most intensive exciton band shifts towards the low energies and its structure becomes more complicated. PL bands at 1.984 and 2.246 eV, intensities of which depend on Ag content in the doping melt, appear in the long-wave region of the spectrum. Both bands are excited by radiation from the impurity absorption region. The nature of radiative centers, its structure and the mechanisms of radiative recombination are discussed on the ground of complex investigation of FL, PLE spectra, lux-brightness characteristics and temperature quenching features of the observed bands. (C) 1999 Elsevier Science B.V. All rights reserved.