Surface photovoltage analysis of copper in p-type silicon

Surface photovoltage minority carrier lifetime/diffusion length analysis of copper-doped p-type silicon was performed. Minority carrier recombination behavior of the deep level induced by copper and its thermal stability in the temperature range of 25–300 °C was investigated. This defect is attributed to interstitial copper pairs in p-type silicon. Isochronal annealing to a temperature of 150 °C results in improvement in diffusion length. This change in recombination behavior is attributed to precipitation of copper. At temperatures higher than 150 °C, copper forms extended substitutional defects in silicon, which results in a decrease in diffusion length. Interstitial copper concentration is estimated using the change in recombination behavior with isochronal annealing. Since copper is known to precipitate rapidly during cooling from high temperatures, it is observed that less than 0.01% of the total copper dissolved in silicon occupies an interstitial position.