Spatially localized band-gap renormalization and band-filling effects in three growth-interrupted multiple asymmetric coupled narrow quantum wells

Abstract

For the first time to our knowledge, we have observed a large excitonic linewidth broadening at low temperatures in three growth-interrupted asymmetric coupled GaAs/Al0.3Ga0.7As narrow quantum wells as the irradiance increases. We attribute this broadening to the decrease of the exciton binding energy that results from spatially localized band-gap renormalization. We also observed the stepwise saturation of the photoluminescence emission peaks as irradiance increases. We attribute this saturation to the result of spatially localized band filling. Based on time-resolved photoluminescence measurements, we have determined the nature of the recombination processes. We have also determined the exciton densities. In both undoped and modulation-doped samples, the small interface island area that results from growth interruption allows us to generate a large carrier density in the islands; both band-gap renormalization and band-filling effects become stronger even at low irradiances. When the temperature is higher than the transition temperature, the free-carrier recombination dominates the photoluminescence spectrum. The band-gap renormalization then results in a red shift of the photoluminescence emissions.