Electron-paramagnetic-resonance study of a deep Cl-associated center in ZnTe: Cl

Abstract

We describe EPR studies of ZnTe doped with chlorine. The characteristic EPR spectrum is observed under optical illumination at low temperature. A defect, which has a trigonal symmetry, is identified as ${\mathrm{Cl}}^{-}$ occupying a tellurium site associated with a positively charged ion which is tentatively assumed to be a ${\mathrm{Sn}}^{2+}$ or a ${\mathrm{Pb}}^{2+}$ ion. Under illumination, the associated defect should become paramagnetic by trapping an electron. Super-hyperfine-splitting lines are also observed and account for the Te nuclei. The Hamiltonian parameters of the center have been obtained. Luminescence, thermoluminescence, and optically detected magnetic-resonance experiments on the same crystals lead to the conclusion that part of the chlorine impurity behaves as a hydrogenic shallow donor but some of the chlorine atoms also form the ${\mathrm{Cl}}^{2-}$ associate center which is a deep center.