Precipitation of Cu in Ge. III. Quench Effects in Nearly Perfect Crystals

Studies have been made of the effects of rapid quenching upon the precipitation rate of Cu in Ge. It is shown that electrically active metastable centers with energies very near the valence band are formed in the early stages of heat treatment of Cu-doped Ge at 500°C and below. These centers are found in concentrations up to ∼${10}^{15}$/${\mathrm{cm}}^3$ in samples with few dislocations. Their stability is very much greater in quenched samples than in slow-cooled specimens, and it increases with decreasing temperature. Evidence also is presented for the formation at the beginning of heat treatment of electrically neutral centers. The presence of metastable centers can completely determine the precipitation kinetics in quenched samples with low dislocation density at temperatures below approximately 425°C.