Fermi-edge singularity in the luminescence spectra of II-VI modulation-doping quantum wells

The occurrence of correlation enhancement at the Fermi edge is demonstrated in the luminescence spectra of modulation-doped ${\mathrm{Zn}}_{1\mathrm{-}\mathrm{x}}$${\mathrm{Cd}}_{\mathrm{x}}$Se/ZnSe quantum wells. The Fermi-edge singularity (FES) is observed at low temperature and is rapidly quenched with increasing temperature. A line-shape analysis reveals that recombination involves momentum-nonconserving transitions between electrons and localized holes. The temperature increase causes thermal activation of the trapped carriers and the consequent recovery of the momentum-conserving recombination. Many-body analysis of the FES line-shape indicates a characteristic localization length of about 14 nm for the holes, which we associate with compositional fluctuations in the ternary alloy quantum wells.