Photoluminescence transitions of GaAs/AlGaAs asymmetric double-well structures

We measured photoluminescence emission spectra from GaAs/AlGaAs semiconductor heterostructures in which asymmetric two-dimensional quantum wells are separated by a thin barrier in the conduction band while the valence band has single square quantum well connected to the GaAs flat band with a thin barrier. In such structure the tunneling barrier generates two subband located energetically in close proximity in the conduction band while the valence band does not have such tunnel-coupled energy gap. Therefore, the photogenerated valence holes tend to move to GaAs flat band region. With low external excitation power, only the interwell optical transitions occur. However, this asymmetric quantum structure shows intense photoluminescence emission behavior with increasing external excitation power. With increasing laser power, simply the number of photogenerated holes near the interface increase and they recombine with the conduction electrons which shows non-linear emission behavior.