Interstitial carbon formation in irradiated copper-doped silicon

The influence of a copper impurity on the spectrum of defects induced in $p$-Si crystals containing a low oxygen concentration by irradiation with electrons with an energy of 5 MeV at room temperature is studied by deep-level transient spectroscopy. It is found that interstitial carbon atoms (C$_i$) which are the dominant defects in irradiated samples free of copper are unobservable immediately after irradiation, if the concentration of mobile interstitial copper atoms (Cu$_i$) is higher than the concentration of radiation defects. This phenomenon is attributed to the formation of $\{$Cu$_i$, C$_i\}$ complexes, which do not introduce levels into the lower half of the band gap. It is shown that these complexes dissociate upon annealing at temperatures of 300–340 K and, thus, bring about the appearance of interstitial carbon.