Localized Excitons in the Spectrum of Optical Absorption of Zinc Oxide Doped with Manganese

The results of the study of optical absorption and EPR signals of single crystals of zinc oxide doped with manganese are presented. A broad impurity absorption band with the threshold energy about 2.1 eV, which was treated as a result of charge transfer transitions, has been observed for a long time in ZnO : Mn absorption spectra. In absorption spectra of a polarized light at 4.2 and 77.3 K, we first detected several lines of different intensity in a 1.877–1.936 eV range of energies of the light quanta. The observed lines are attributed to a donor exciton [(d⁵ + h)e] that emerges as a result of the Coulomb binding a free s electron and a hole, which is localized on p–d hybridized states. The EPR spectra of Mn²⁺ ion signals, when corresponding to the impurity absorption band exposed to light, are found to be not photosensitive. The obtained results indicate that the ZnO : Mn impurity absorption is due to transitions from antibonding p–d hybridized DBH states to the conduction band.