Electronic structure and migrational properties of interstitial zinc in ZnSe

We report optically detected electron paramagnetic resonance via photoluminescence in ZnSe after in situ 4.2 K irradiation with 2.5 MeV electrons. The isolated interstitial is identified in the Td site surrounded by four zinc atoms, (Zn-i)(Zn)(+), as well as in the T-d site surrounded by four Se atoms, (Zn-i)(Se)(+). Analysis of the central Zn-67 and neighboring Se-77 atom hyperfine interactions for the two sites, plus other considerations, allows estimates of their second donor levels to be at similar to 1.6 and similar to 1.0 eV below the conduction band, respectively. Migration of the interstitial under optical excitation at 1.5-25 K is detected by monitoring its cyclic conversion between the two configurations, as well as by interconversion between various close zinc-interstitial-zinc-vacancy Frenkel pairs. The dependence of the process on temperature. excitation wavelength and intensity, and sample history is described, and a possible model for the mechanism is proposed.