The formation of photoluminescence Cu centres (1.014eV) was observed in crystals which had been diffused with Cu at 700C. In the case of samples with Cu concentrations lower than 1014/cm3, almost the same numbers of Cu centres were created (without forming Cu precipitates) - for a given Cu concentration - for all of the cooling conditions which were used. The Cu center was very stable for long storage periods at room temperature. More frequent Cu precipitation occurred in samples with higher Cu concentrations. Quenching of the equilibrium states of the Cu complexes at high temperatures did not occur during rapid cooling. The thermal equilibria and stability of Cu complexes, for samples which contained no Cu precipitates, differed from those of samples which contained precipitates.

Thermal Equilibrium and Stability of Copper Complexes in Silicon Crystal M.Nakamura: Applied Physics Letters, 2000, 76[15], 2089-91