The thermal dissociation of Cu pairs was studied in p-type samples. The dissociation energy of the Cu pair was found to be 1.02eV. This was twice as high as the binding energy of a Coulombically bound donor-acceptor pair placed on nearest-neighbor <111> sites. This implied that the pair was either covalently bonded, or consisted of an ionically bonded doubly negatively-charged acceptor and a singly charged donor. In order to distinguish between these 2 models, the dependence of the hole emission rate upon the electric field in the depletion region was studied. The absence of Poole-Frenkel emission enhancement ruled out an acceptor nature for the center and purely ionic-type bonding. On the other hand, a polarization potential which described emission from a neutral impurity gave a satisfactory fit to the experimental data. It was concluded that the Cu pair was a donor with either covalent or mixed-type bonding.

A.A.Istratov, H.Hieslmair, T.Heiser, C.Flink, E.R.Weber: Applied Physics Letters, 1998, 72[4], 474-6