Radiative properties of n-ZnSe single crystals doped with Ag

Abstract

Ag impurity exists in ZnSe as interstitial atoms Ag<SUB>i</SUB> and substitution atoms Ag<SUB>zn</SUB>. The structure of photoluminescence (PL) spectra of the ZnSe crystals doped with Ag depends on quantitative ratio of these defects in the crystal. Evidently, this is a cause of significant difference of PL spectra of n-ZnSe crystals doped with Ag either in the growing process or in the process of annealing in the Zn+Ag melt. The questions of electron configuration and of a charge state of Ag impurity in ZnSe is discussed also in the literature. Theoretical analysis of this problem allows the existence possibility of Ag multi-charged states in ZnSe, while the authors assume that Ag in ZnSe exists only in the single-charged state with d<SUP>10</SUP>-electron configuration. In this work, the PL spectra and photoluminescence excitation (PLE) spectra of n-ZnSe single crystals annealed in Zn melt with Ag contents from 0.1 at.% to 20 at.% are investigated in the temperature range from 82 K to 300 K. The annealing was made at the temperature of 950 degrees Celsius during the 100 h. At the termination of annealing the quartz ampoules were immersed in cold water for the sharp cooling of the samples. Luminescence was excited either by radiation of LGI-21 laser with the wavelength of 337 nm (E<SUB>excit</SUB> equals 3.68 eV) or by monochromatic light from VSU-1 monochromator with the halogen lamp. The investigation of PL spectra was carried out using MDR-23 monochromator with the line dispersion of 1.4 nm/mm in the wavelength region from 430 nm to 700 nm.