Influence of interstitial copper on diffusion length and lifetime of minority carriers in p-type silicon

Though copper can be quenched interstitially in p-type silicon, it precipitates completely within 10–15 h at room temperature. The decay of concentration of interstitial copper in p-Si was monitored by capacitance–voltage characteristics (C–V) and surface photovoltage (SPV). It is shown that the time constant of change of minority carrier diffusion length, as measured by SPV, correlates well with the precipitation of interstitial copper. The capture cross section of interstitial copper is estimated to be in the range 10−15–10−17 cm2. It is shown that interstitial copper is far less deleterious than iron and can limit the diffusion length of commercial p-Si wafers only if its concentration is above 1013 cm−3. However, copper precipitates may be detrimental to lifetime even for much lower copper concentrations.