Influence of light on interstitial copper in p-type silicon

In this work, the influence of light absorption on copper related defect reactions in p-type silicon is investigated by transient ion drift measurements. It is found that copper out-diffusion and formation of copper complexes are two competitive processes whose relative importance depends on light intensity. At low intensities, a reduced surface potential allows complete copper out-diffusion. Above a certain threshold value, however, copper complexes are formed which could be responsible for the earlier reported optically activated recombination activity of copper in silicon. It is shown that the observed Fermi-level dependence of the defect formation rate cannot be explained in terms of an optically induced change in the interstitial copper charge state. The high thermal stability of the formed copper complexes further points out that the formation of electrostatically bound copper-defect pairs may be ruled out. PACS 61.72.Cc; 61.72.Ss; 66.30.Jt