The electronic structure, stability, and chemical trend of cation interstitials in II–VI semiconductors were studied through ab initio methods. It was found that interstitials in the neutral charge state were more stable in the tetrahedral interstitial site near to the cation whereas, in the (2+) charge state, they were more stable near to the anion. This bistability was explained through the Coulomb coupling and energy-level repulsion in the two different interstitial sites. It was shown that the diffusion energy barrier changed when the defect charge state changed. It was suggested that, if electrons or holes were taken from the defect level by light, changing its charge state, the interstitial atom would be able to diffuse almost spontaneously due to a reduced diffusion barrier. These results could help to clarify the nature of the recently observed photo-induced migration of interstitials in II–VI semiconductors.

Photo-Induced Cation Interstitial Diffusion in II–VI Semiconductors. G.M.Dalpian, S.H.Wei: Physical Review B, 2005, 72[7], 075208 (5pp)