Photoluminescence in delta-doped InGaAs/GaAs single quantum wells

We have studied the time integrated (cw) and time resolved photoluminescence (PL) spectra of Si δ-doped In_0.2Ga_0.8As/GaAs quantum wells (QWs), in which the δ doping layer was either at the center of the quantum well or outside the well, in the barrier region. We found that both the cw and the time resolved PL depended significantly on the position of the doping sheet. When the doping was at the center of the quantum well the luminescence spectrum displayed the characteristic features of the Fermi edge singularity, while in the case of barrier-doped QW, the PL spectra showed well-defined emission lines originating from transitions between subbands in the conduction and valence bands. From low-temperature time resolved PL experiments, we determined the effective hole capture times, the interband relaxation times (for holes), and the radiative decay times for both types of doping. We found that the interband relaxation time in the center-doped QWs is nearly two orders of magnitude shorter (τ=3 ps) than in samples doped in the barrier (τ= 200 ps).