SPATIALLY LOCALIZED BAND-GAP RENORMALIZATION AND BAND-FILLING EFFECTSIN 3 GROWTH-INTERRUPTED MULTIPLE ASYMMETRIC COUPLED NARROW QUANTUM-WELLS

For the first time to our knowledge, we have observed a large excitoni c linewidth broadening at low temperatures in three growth-interrupted asymmetric coupled GaAs/Al(0.3)Gao(0.7) As narrow quantum wells as th e irradiance increases. We attribute this broadening to the decrease o f the exciton binding energy that results from spatially localized ban d-gap renormalization. luminescence emission peaks as irradiance incre ases. localized band filling. Based on time-resolved photoluminescence measurements, we have determined the nature of the recombination proc esses. We have also determined the exciton densities. In both undoped and modulation-doped samples, the small interface island area that res ults from growth interruption allows us to generate a large carrier de nsity in the islands; both band-gap renormalization and band-filling e ffects become stronger even at low irradiances. When the temperature i s higher than the transition temperature, the free-carrier recombinati on dominates the photoluminescence spectrum. The band-gap renormalizat ion then results in a red shift of the photoluminescence emissions. (C ) 1996 Optical Society of America