MODULATED ENERGY RELAXATION OF PHOTOEXCITED CARRIERS INTO THE EXCITONIC GROUND-STATE IN SHALLOW INXGA1-XAS/GAAS QUANTUM-WELLS

Time-resolved and time-integrated investigations were performed with a systematic variation of the excitation energy to study the energy transfer process of photoexcited carriers into the excitonic ground state in shallow InxGa1-xAs/GaAs quantum well heterostructures. For an excitation above the GaAs bandgap, a modulation of the transfer time and, in counter-phase, oscillations of the photoluminescence intensity were observed by varying the excitation energy, reflecting the influence of LO-phonon scattering on the electron transfer process from the barrier into the excitonic ground state of the quantum well. For excitation energies below the barrier bandgap, a resonant excitation of light hole excitons in the well or free excitons in the GaAs barrier causes a significant generation of hot heavy, hole excitons in the quantum well. We observe a distinct enhancement of the transfer time due to the increased relaxation time of hot excitons into the K=0 ground state.