Recombination dynamics of spatially separated electron-hole plasmas in GaAs/AlAs mixed type-I/type-II quantum well structures

We have studied the recombination dynamics of a series of mixed type-I/type-II GaAs/AlAs quantum well structures. While monitoring the recombination involving the wide quantum wells, we observed long-lived transients whose time scales increase exponentially with the barrier thickness of the quantum well structures. We identify heavy hole tunneling as the dominant process which determines the time scale of the long-lived photoluminescence transients. By studying the barrier thickness dependence and the excitation power dependence of the long-lived transients we have also shown that the electric field associated with the spatially separated electron/hole plasma leads to significant modifications of the relative hole subband energies and hence the hole tunneling rate.