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Session O21 - Mesoscopics: Optical Properties (Excitons).
MIXED session, Thursday afternoon, March 21
Room 263, America's Center
We have observed "hot" luminescence (HL) from excited states in the magneto-optical spectra of quantum dots, where carriers in a GaAs/AlGaAs quantum well are laterally confined by inhomogeneous strain. The dependence of the HL on excitation intensity is unusual. When there is less than one exciton per dot, the HL is strong. We attribute this phenomenon to slow energy relaxation via phonon emission, which is inhibited by the discrete density of states in the quantum dot because the confined excitons are spatially too large to couple to phonons with the inter-subband energy.(U. Bockelmann, Phys. Rev. B 48, 17637 (1993).) The effect is not observed in strain-induced quantum wires, and the relaxation rate in the dots is at least two orders below that of the host quantum well, where the density of states is continuous. When the average carrier density exceeds two electron-hole pairs per dot, the HL weakens considerably because carrier-carrier interactions accelerate relaxation by the Auger effect.
