Intensity correlated nonlinear photoluminescence spectra in undoped and p-doped GaAs and GaAs quantum wells

We study the line shapes and excitation density dependence of the intensity correlated nonlinear (NL) photoluminescence (PL) spectra due to excitons and free electron-hole pairs in molecular beam epitaxy grown undoped and p-doped GaAs and GaAs quantum wells. The laser excitation intensity (I) is varied by nearly three orders of magnitude. The NL PL spectra show negative peaks at energies corresponding to free and bound excitons as I increases. These peaks do not diminish, but continue to increase with I up to the highest value of I used.