Thick AlxGa1−xAs: An intrinsically percolating barrier owing to its microscopic structural inhomogeneity

A significant charge transfer, which differs from tunneling, over thick AlxGa1−xAs barrier in GaAs/AlxGa1−xAs asymmetric double quantum wells is studied by cw photoluminescence excitation (PLE) and time‐resolved photoluminescence. It is found that 300‐A‐thick Al0.3Ga0.7As barrier is universally ‘‘leaky’’ with transport time of ∼300 ps, while AlAs and AlAs/GaAs digital alloy barriers with same thickness are not. Aided by a model calculation, we suggest that the intrinsic inhomogeneities in the alloy, which recent x‐ray and scanning tunneling microscope studies revealed, may be responsible.