Electron-density-dependent optical spectra of a remotely-doped GaAs/Al 0.33Ga 0.67As single quantum well

We have measured electroreflectance (ER) and photoluminescence (PL) spectra of a high-quality remotely-doped GaAs/Al 0.33Ga 0.67As quantum well (QW) as a function of electron density. Both techniques show the transition from the electron Fermi energy to the ground hole subband, although it is enhanced in ER due to its strong blue shift with electron density. The negligible Stokes shift of the transition demonstrates that the holes involved in the recombination are not strongly localised, consistent with the absence of a distinct peak due to the Fermi edge singularity. The ER spectra show in addition several transitions from the Fermi energy to excited hole subbands. Transitions involving the second and third electron subbands shift to lower energy with electron density due to both the Stark shift induced by the charge in the QW and bandgap renormalisation, which we compare to calculations.