Abstract
The optical properties of p-type modulation doped GaAs/AlGaAs quantum wells have been investigated for acceptor concentrations in the high doping regime by means of photoluminescence (PL) and PL excitation. Several novel physical effects have been observed as the hole density increases. The main effect is a significant red-shift of the main emission due to the bandgap renormalization caused by many-body effects. The observed renormalization is compared with theoretical predictions of the effective bandgap shrinkage, based on self-consistent calculations. Another apparent observation at high hole densities is the exciton quenching. The acceptor doping level required to quench the excitons is found to be significantly lower than for the case with acceptor doping inside the well, but on the other hand, considerably higher than that one in the bulk case, due to the inefficiency of screening in a 2D system. Finally, we report on the observation of a new feature, the Fermi edge singularity (FES), i.e. the transition between 2D holes at the Fermi edge and free electrons. The dynamical behavior of the FES has been investigated by means of time-resolved PL, showing a relatively short decay time as well as rise time for the FES emission.
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