Stimulated-Picosecond-Photon-Echo Studies of Localized Exciton Relaxation andDephasing in GaAs/Al(x)Ga(1-x)As Multiple Quantum Wells

摘要

We report measurements of the dynamics of localized excitons in GaAs/Al(x)Ga(1-x)As multiple quantum well structures at low temperature based on stimulated-picosecond-photo echo measurements. The results show that at low temperature excitons relax by phonon-assisted migration between localization sites and at higher temperatures are thermally activated to delocalized states. The measurements confirm recent theoretical predictions, but show the unexpected presence of additional dephasing. The effect of disorder caused by nonideal growth conditions in multiple quantum wells (MQW's) on optically excited electronic states in solids has been the subject of recent interest in studies of excitons. Transport and chemical lattice imaging measurements show that interface roughness is due to island formation, typically one monolayer high with a lateral dimension on the order of 50 angstroms.