EFFECT OF THE X POINT ON THE ESCAPE OF ELECTRONS FROM THE QUANTUM-WELL OF A DOUBLE-BARRIER HETEROSTRUCTURE

We describe a photoluminescence study of a series of GaAs/AlAs/GaAs/AlAs/GaAs double-barrier heterostructures. We report the observation in double-barrier heterostructures of photoluminescence from the recombination of electrons at X-point levels localized in the AlAs barriers, with heavy holes localized in the GaAs quantum well. As the quantum-well width is decreased, the increasing confinement energy of the GAMMA-point electron level in the quantum well results in increasing interaction with the X-point levels in the barriers. As the well width is decreased, the integrated GAMMA-point photoluminescence intensity decreases, and then increases just before the GAMMA-X crossover; further decrease in the well width results in monotonic decrease of intensity. This behavior is consistent with eight-band tight-binding calculations of the GAMMA-point electron quasi-bound-state lifetime.