Evidence on a bond-breaking relaxation in the bistable centers In and Ga in CdF2

Positron annihilation experiments reveal an open-volume defect in the deep state atomic configurations of bistable donors In and Ga in CdF2. The size of the open volume is at least half of a monovacancy. The results are simil ar to those obtained previously for the DX centers in the covalent system A lxGa1-xAs. It is therefore likely that the bond-breaking mechanism (substit utional to interstitial atomic motion) responsible for metastability of poi nt defects in covalent semiconductors is more universal and its validity ex tends to even some highly ionic compounds, like CdF2. (C) 1999 Elsevier Sci ence B.V. All rights reserved.