Spatially-Localized Band-Filling Effects and Band-Gap Renormalization in Growth-Interrupted Quantum Wells

We have observed a large excitonic linewidth broadening at low temperatures in growth-interrupted asymmetric-coupled quantum wells as irradiance increases. We attribute this broadening to the decrease of the exciton binding energy due to spatially-localized bandgap renormalization. We have also observed the stepwise saturation of the photoluminescence emission peaks as irradiance increases in growth-interrupted asymmetric-coupled quantum wells with various structures and doping profiles. We attribute this saturation to the result of spatially-localized band-filling effects. Based on the time-resolved photoluminescence measurements, we have determined the nature of the recombination processes and the exciton densities. In both undoped and modulation-doped samples, the small interface island area as a result of growth-interruption allows us to generate large carrier density in the islands; both band-gap renormalization and band-filling effects become stronger even at low irradiances. In compensation-doped asymmetric-coupled quantum wells, we observed anomalously large blue shift of donor-acceptor pair transition energy as the laser intensity increases.