Influence of degenerate free carriers on radiative lifetimes in GaAs quantum wells

The influence of the Coulomb interaction on the radiative recombination rate of minority photocreated carriers in a GaAs quantum well containing a degenerate free-electron or hole gas at 1.8 K is investigated using time-resolved photoluminescence. A factor of \ensuremath{\approxeq}1.5 enhancement in the recombination rate compared to that expected without the Coulomb interaction is observed experimentally at a carrier density of 8\ifmmode\times\else\texttimes\fi{}${10}^{10}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}2}$. The recombination rate is also calculated theoretically as a function of carrier density and minority carrier localization in the presence of the Coulomb interaction. An enhanced rate is obtained due to correlation between the degenerate Fermi gas and the minority carrier at the Fermi edge, but only when the minority carrier is localized. The degree of localization required to reproduce the experimental data is determined.