Resonant electron capture in AlxGa1-xAs/AlAs/GaAs quantum wells.

Abstract

Resonant electron capture in ${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$As/AlAs/GaAs quantum-well structures is systematically investigated by means of both continuous-wave and time-resolved photoluminescence. The capture efficiency and the capture time of barrier electrons into quantum wells both exhibit a clear oscillation as a function of well width. The enhanced capture efficiency in the oscillation is ascribed to the resonant electron capture. It is also revealed that the resonant effect is drastically enhanced by the insertion of AlAs tunnel barriers at both heterointerfaces and controlled by their widths. The resonant well width can be well described within the framework of the effective-mass approximation. An oscillating capture time due to the resonant electron capture is observed between 175--480 and 43--270 psec for 20- and 10-\AA{} tunnel barriers, respectively. Investigation of the temporal profile of the quantum-well luminescence suggests ambipolar capture of the carriers due to the charge buildup effect.