Enhancement of free-to-bound transitions due to resonant electron capture in Be-doped AlGaAs/GaAs quantum wells

We report a new phenomenon concerning the photoluminescence (PL) from AlxGa1-xAs/GaAs (x = 0.31) quantum wells with Be-delta-doping at the well center. For excitation photon energy larger than the barrier band gap, the PL intensity ratio between the free-to-bound and the excitonic transitions was found to display a strong oscillation as a function of the well width. For "resonant" well widths, the free-to-bound transition was observed to be 2.3 times as strong as the excitonic transitions. We correlate this phenomenon with the electron capture efficiency from the barrier into the well, which also exhibits a similar oscillation as a function of the well width. © 1994.