Fermi edge singularity and screening effects in the luminescence spectra of Si or Be delta-doped GaAs.

Single Si or Be Delta-doped layers in GaAs have been investigated by photoluminescence (PL) and photoluminescence excitation spectroscopy (PLE). Strong radiative recombination is observed from the two-dimensional electron or hole gas when the photocreated minority carriers are confined by GaAs/AlsubxGasub1minusxAs heterointerfaces placed at both sides of the doping spike. In n-type Delta- doped structures the low-temperature PLE spectrum shows a well resolved Fermi edge enhancement with the energy position of the absorption edge independent of the excitation intensity. The spatially indirect band-to-band recombination, in contrast, is found to shift to higher energies with increasing excitation intensities due to screening of the space charge induced potential by photogenerated carriers. In the p-type Delta-doped structure the low-temperature emission from the two- dimensional hole gas shows a pronounced enhancement in intensity at the Fermi edge.