Electron paramagnetic resonance via photoluminescence methods were used after in situ irradiation with 2.5MeV electrons at 4.2K. Isolated interstitials were detected in the Td sites surrounded by four Zn atoms, (Zni)Zn+, as well as in the Td sites surrounded by four Se atoms, (Zni)Se+. An analysis of the central 67Zn and neighbouring 77Se atom hyperfine interactions for the 2 sites suggested that their second donor levels were at about 1.6 and 1.0eV below the conduction band, respectively. Migration of the interstitial, under optical excitation at 1.5 to 25K, was detected by monitoring the cyclic conversion between the 2 configurations, as well as interconversion between various close Zn-interstitial plus Zn-vacancy Frenkel pairs.

Electronic Structure and Migrational Properties of Interstitial Zinc in ZnSe K.H.Chow, G.D.Watkins: Physical Review B, 1999, 60[12], 8628-39