RESONANCE EFFECTS IN THE CARRIER-TUNNELING DYNAMICS IN ASYMMETRIC COUPLED QUANTUM-WELLS

We present a detailed experimental study of the tunneling times, after picosecond excitation, of electrons and holes in a large set of unbiased GaAs/AlxGa1-xAs asymmetric double-quantum-well structures, pointing out the role played by resonances in the tunneling process. In particular, fast hole tunneling is found when the quantum wells show band alignment both at k parallel-to = 0 and at k parallel-to not-equal 0. Referring to electrons, a resonance is found in the tunneling time, which corresponds to phonon-assisted processes. Experimental data at high excitation intensity are also reported, suggesting band-filling effects in the wider well.