Time-resolved photoluminescence spectra after nonresonant excitation show a distinct 1s resonance, independent of the existence of bound excitons. A microscopic analysis identifies excitonic and electron-hole plasma contributions. For low temperatures and low densities the excitonic emission is extremely sensitive to even minute optically active exciton populations making it possible to extract a phase diagram for incoherent excitonic populations.
@article{arxiv.cond-mat/0309160,
title = {Excitonic Photoluminescence in Semiconductor Quantum Wells: Plasma versus Excitons},
author = {S. Chatterjee and C. Ell and S. Mosor and G. Khitrova and H. M. Gibbs and W. Hoyer and M. Kira and S. W. Koch and J. P. Prineas and H. Stolz},
journal= {arXiv preprint arXiv:cond-mat/0309160},
year = {2009}
}