A theoretical study of the trapping behavior of defect clusters in semiconductors indicates that many of the unusual trapping effects observed in neutronhyphen;irradiated materials are a natural result of placing a large density of otherwise normal deep defects within a defect cluster. The space charge which results from majority carriers trapped on such defects within the cluster produces a potential barrier for majority carriers, or a potential well for minority carriers, which greatly influences the capture kinetics of defects within the cluster. Approximate calculations have been performed for the buildhyphen;up of charge within the cluster following a large pulse of injected minority carriers. The calculations predict that the excess conductivity produced by this pulse should decay at an extremely slow nonexponential rate, especially at low temperatures. The predictions are in good agreement with experimental results for photoconductive decay in neutronhyphen;irradiated silicon.
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