Unraveling the μτ-mystery in a-Si:H

The μτ-mystery is the large difference between mobility-lifetime products (μτ) in a-Si:H estimated from steady-state photoconductivity and transient photocharge measurements. We discuss whether this effect can be attributed to deep-trapping of electrons and subsequent re-emission prior to recombination. We present a simplified version of the re-emission model which shows that its principal assumptions can be checked using photocharge measurements over a sufficiently large time range. Measurements of the transient photocharge in a-Si:H are presented between 10−8 and 102 s; the measurements show the same features as the re-emission model, and permit the characteristic emission time to be measured.