n-type silicon samples were measured by deep level transient spectroscopy (DLTS) immediately (within one hour of storage at room temperature, required for the preparation of Schottky-diodes) after copper diffusion and quench. A donor level atEc-(0.15±0.01) eVwith a concentration of up to1013 cm−3was detected. The amplitude of the DLTS peak decreased with the time of storage at room temperature, and stabilized at a concentration(4 to 7)×1011 cm−3after 15–20 h. The activation energies and prefactors of the decay of the DLTS peak inn-type Si and the reactivation of copper-compensated boron inp-type Si concur. This correlation suggests that the deep level is interstitial copper itself or a complex of interstitial copper. ©1997 American Institute of Physics.