Carrier lifetimes in amorphous silicon junctions from delayed and interrupted field experiments

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Abstract
Transient methods in which the internal field is delayed after photogeneration or interrupted during carrier transit are applied to the study of excess electron and hole lifetimes, τe and τh, in a-Si p-i-n junctions, between 1 μm and 11μm thick. After the delay, carrier extraction occurs in a strong applied field, so that the results are unaffected by non-uniformity in the internal junction field. The results lead to thickness-independent values of the lifetimes τe≡0.6 μs and τh≡10ms, which represent material properties of undoped a-Si. It is concluded that the systematic thickness dependence of τ and μτ values observed in previous work arises from a field limitation in the thinner specimens. Results on the temperature dependence of τe are included in the paper.