The presence of Cu atoms in p-type material was revealed via their characteristic electric field gradients, which were measured at the radioactive acceptor, 111In/111Cd, via the perturbed γ-γ angular correlation technique. The Cu formed pairs with acceptor atoms and electrically passivated them. By using known Cu diffusion data and taking account of the effect of ion-pairing, an activation energy of 0.15eV was deduced. This value was in accord with the energy of 0.70eV which had been deduced for Coulomb-bound acceptor-Cu pairs.

Copper in Silicon. R.Keller, M.Deicher, W.Pfeiffer, H.Skudlik, D.Steiner, T.Wichert: Physical Review Letters, 1990, 65[16], 2023-6