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Excitons confined to CdSe͞ZnSe self-assembled quantum dots are probed through a nanoaperture using time-resolved photoluminescence. Significant evidence is shown that two different electronic states are associated with these dots, with binding energies which differ by an order of magnitude. The first has a short 450 ps lifetime, exhibits a relatively broad emission line, and persists nearly to room temperature; the second exhibits a long ͑.4 ns͒ lifetime and is responsible for the sharp ͑ϳ100 meV͒ lines seen at low temperatures ͑,60 K͒. These results are completely unlike those seen in III-V dots, and reveal the complexity of the electronic structure in CdSe dots. PACS numbers: 71.55.Gs, 78.47. + p, The past decade has seen a surge of effort in developing methods for confining electronic states in semiconductors to less than two dimensions. One of the most effective methods has been the growth of self-assembled quantum dots (SAQDs) which are formed when the large lattice strain between two different semiconductor layers is relieved to form well-defined pyramids or domes across the epitaxially grown surface; examples are InAs on GaAs [1], or more recently, CdSe on ZnSe [2][3][4]. Many experiments over the past six years have shown that these structures strongly confine electrons and holes, and result in nearly a zero-dimensional density of states. More recently, intense efforts have been directed toward understanding the internal electronic structure of these quantum dots (QDs), and how this structure changes with the various material systems. Theoretical calculations which include the effects of strain on these structures have shown that the confined electronic states can be quite complex, with electrons or holes separately confined to regions on the perimeter or interior of the quantum dots [5].In this Letter, we present temporally and spatially resolved photoluminescence (PL) experiments on CdSe͞ZnSe self-assembled quantum dots which show directly that there are two different types of electronic states associated with these QDs with radically different binding energies and electron-hole wave functions. Moreover, these results show clearly that the character of these electronic states is significantly different than has been observed in the InP͞InGaP or InAs͞GaAs QD systems.Because of its sensitivity to electron and hole wave function overlap, time-resolved (TR) photoluminescence can be a powerful tool for probing the internal electronic structure of QDs. A number of macro-PL measurements on a .30 mm length scale have shown approximately 0.5-1 ns lifetimes which are weakly temperature dependent [6][7][8][9][10][11]. More recently, Zwiller et al. have shown spatially and temporally resolved m-PL of InP͞GaInP QDs which displayed relatively sharp (3 meV wide) spectral features [12]. However, these experiments also did not show significant distinction in the lifetimes of the different spectral features.In this Letter, we report the first measurement of time-resolved PL through a 200 nm aperture which shows directly ...

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We report resonant photoluminescence from CdSe/ZnSe self-assembled quantum dots. When CdSe quantum dots are resonantly excited, excitonic sharp micro-photoluminescence peaks originating from individual quantum dots are strongly enhanced in the region corresponding to optical phonon energies below the excitation. The phonons active in this process are identified as the longitudinal optical ͑LO͒ phonons from the CdSe dots, as the interface phonons, and tentatively as the LO phonons from the two-dimensional-like precursor layers. These observations suggest that exciton recombination via phonons is a major relaxation process under resonant excitation.