Abstract
During molecular-beam epitaxy, growth interruption at each heterointerface of single quantum wells results in very narrow multiple peaks in photoluminescence (PL) spectra. These peaks correspond to extended monolayer-flat regions of the wells, differing in well thickness by one monolayer. PL and PL-excitation spectroscopies show that excitons tend to diffuse from narrower-well regions to thicker-well regions before radiative recombination takes place. This is also observed in time-resolved PL. The intensity of the higher-energy peak decreases with time, while that of the lower-energy peak increases with time. The obtained exciton diffusion time of ≂250 ps is in good agreement with the estimated size (≤1 μm)of the monolayer-flat islands from spectrally resolved cathodoluminescence.
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