Abstract
We report on the selective excitation of photoluminescence (PL) and resonant Raman scattering (RRS) study of two multi-quantum well (MQW) structures at T=2K. Both structures consist of 10 GaAs wells separated by 200 Å of Al 0.28Ga 0.72As barriers grown by MBE. One MQW was grown in an uninterrupted growth process while the other was grown with 40 seconds interruption at each of the interfaces. Both samples show inhomogeneously broadened luminescence bands, with a characteristic splitting due to “interface islands” in the interrupted growth sample. Selective excitation into its low energy tail reveals spectral diffusion indicative of localized excitons. The RRS by LO phonons shows an enhancement of the scattering efficiency at the outgoing beam which is 20-fold stronger than that of the incoming one. The peak energy and band width of the RRS profile reflect the extended excitons density of states. This is interpreted in terms of resonance enhancement by exciton scattering by interface potential fluctuations.
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