Screening and correlation effects in degenerately center doped GaAs/AlGaAs single quantum wells.

The effects of correlation and screening in modulation doped quantum wells have received considerable recent interest. Equivalent interactions have, however, not been discussed for center doped structures. We have investigated the dependence of the photoluminescence spectra upon excitation for an "n-type" single quantum well degenerately center doped. An enhancement of the excitation spectra in the vicinity of the Fermi level is observed. This enhancement shows an equivalent dependence on temperature and excitation dependence as has been discussed for the Fermi edge singularity. We therefore associate this effect with many-body type interactions. The dynamic response of the photoluminescence has also been studied using a picosecond time-resolved setup. A strong spectral shift (bigger than 10 meV over a period of 1 ns) is found to occur for the peak photoluminescence intensity following excitation at high intensity. We propose that the dependence of the recombination on excitation can b e related to the distribution of occupied hole states, which in turn is dependent on the short time screening of the ionised donor potentials. The enhancement of the excitation spectra in the vicinity of the Fermi level is then ascribed to the relative screening efficiency of electrons excited with this energy.