Minority carrier lifetime of p-type silicon containing oxygen precipitates: influence of injection level and precipitate size/density

The behaviour of minority carrier lifetime in p-type Czochralski silicon co ntaining various concentrations of oxygen precipitates has been investigate d in relationship to precipitate size, which is estimated by means of the r eduction of interstitial oxygen concentration and injection level. The latt er is varied in a wide range by comparing surface photovoltage technique, w hich operates at low injection, and microwave probed photoconductive decay technique, which operates at high injection. It is shown that at high injec tion level, the experimentally observed lifetime dependence on precipitate density and size can be explained, assuming that the recombination process rakes place via silicon-precipitate interface states. However, at low injec tion, it is necessary to also take into account the effect of a fixed posit ive charge at the silicon-precipitate interface, which creates a depletion region around the precipitate, thus increasing its 'effective capture size' . A model is presented, based on these mechanisms, which is in good agreeme nt with the experimental data. (C) 2000 Elsevier Science S.A. All rights re served.