We report experimental evidence for the existence of confined polyexcitons in strain-relaxed epitaxial SiGe layers by means of low temperature photoluminescence. The number of excitons, n, up to 4 in a polyexciton is confirmed. Our data clearly show that only one type of polyexcitons is confined on potential wells generated by lower band gap regions in SiGe layers due to alloy fluctuations. The radiative annihilation of a polyexciton with a given n produces n-1 photons and a single exciton left behind. The most striking fact is that polyexcitons having n > 2 do not decay to polyexcitons have n - 1. These observations can be explained by the quantum effect of indistinguishability of ployexcitons which possess either zero or integral spin. This effect is enhanced in a confined well since confined polyexcitons interact strongly among themselves in a limited spatial region. Our observations are important to understand the unique properties of a few quantum particles in a confined region.
By: Kai Shum, P. M. Mooney, J. O, Chu
Published in: Physical Review B, volume 60, (no 8), pages 5786-90 in 1999
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