OBSERVATION OF RESONANT ELECTRON-CAPTURE IN ALGAAS/GAAS QUANTUM-WELL STRUCTURES

We demonstrate for the first time the experimental evidence for the resonant electron capture in AlGaAs/GaAs quantum wells. The sample used contains thin AlAs tunnel barriers on both sides of the GaAs well layer to enhance the quantum-mechanical reflectivity of the electron. It was found that the capture efficiency of photogenerated electrons in the AlGaAs barrier into the quantized state of the well is strongly depedent on the well width and increases under the resonant condition where the well width is such that the highest quantized state in the well coincides with the conduction-band edge of the AlGaAs barrier. The enhanced capture efficiency under the resonant condition is ascribed to the increased probability that the electron in the continuum state at the barrier band-edge is found in the well.