Evidence for resonant electron capture and charge buildup in GaAs/AlxGa1-xAs quantum wells.

Abstract

Evidence for the resonant capture of electrons into quantum wells (QW's) is demonstrated in the photoluminescence (PL) of GaAs/${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$As QW's doped with Be. We find that the PL intensity ratio between the free-to-bound and excitonic transitions exhibits a strong oscillation as a function of the QW width bearing a striking resemblance to the theoretical prediction of the electron capture rate. It is shown that this PL behavior reflects the buildup of excess negative charge in the QW arising from the different capture efficiencies of electrons and holes. \textcopyright{} 1996 The American Physical Society.