Interisland exciton migration and enhanced bound exciton recombination in an AlGaAs/GaAs quantum well structure grown by molecular beam epitaxy without growth interruptions at interfaces

Abstract

Low-temperature excitonic effects in a high-quality AlGaAs/GaAs single quantum well (25 monolayers wide) structure grown without growth interruptions at the interface were studied using steady-state, time-resolved and photoluminescence excitation spectroscopy. Heavy-hole free exciton and impurity (neutral donor) bound exciton emissions, associated with quantum well regions (islands) 24 and 25 monolayers wide, have been resolved and identified using excitation energy resonant with the heavy-hole exciton energy. Interisland exciton migration, until now reported only for growth interrupted structures, is observed, indicating that islands formation is not a specific property of growth interrupted structures. We estimate the rate of transfer of free excitons between regions of width 24 monolayers and 25 monolayers to be 290 . We show that the relative intensity of free-to-bound excitonic emissions strongly depends on interface morphology and that enhanced bound exciton recombination is observed under some conditions. The relevant mechanisms of such enhanced bound exciton recombination are proposed.