Influence of bound and unbound electron-hole-pair populations on the   excitonic luminescence in semiconductor quantum wells
  A fully microscopic theory for the spontaneous emission from semiconductors is discussed. The theory is evaluated for a quantum-well system and the role of excitonic and unbound electron-hole-pair contributions to the emission is analyzed. Simplifying aproximations to the full theory and their range of validity are discussed. Numerical solutions are presented for experimentally relevant situations and it is shown that a detailed analysis of measured spectra requires the knowledge of both absorption and emission under identical conditions. 
W. Hoyer, M. Kira, and S. W. Koch