Abstract
A set of seven type-II superlattices (T2SLs) are designed to have specific band-gap energies between 290 meV () and 135 meV () in order to study the effects of the T2SL band-gap energy on the minority-carrier lifetime. A temperature-dependent optical pump-probe technique is used to measure the carrier lifetimes, and the effect of a midgap defect level on the carrier-recombination dynamics is reported. The Shockley-Read-Hall (SRH) defect state is found to be at energy of approximately relative to the valence-band edge of bulk GaSb for the entire set of T2SL structures, even though the T2SL valence-band edge shifts by 155 meV on the same scale. These results indicate that the SRH defect state in T2SLs is singular and is nearly independent of the exact position of the T2SL band-gap or band-edge energies. They also suggest the possibility of engineering the T2SL structure such that the SRH state is removed completely from the band gap, a result that should significantly increase the minority-carrier lifetime.
- Received 29 January 2016
DOI:https://doi.org/10.1103/PhysRevApplied.5.054016
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