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We report a detailed experimental investigation of the power dependence of excitonic complexes (neutral exciton, neutral biexciton, and charged exciton) confined in single self-assembled GaAs/AlGaAs strain-free quantum dots grown by droplet epitaxy. By using the random population theory we show that, under stationary excitation, the power dependence of the excitonic complexes precisely follows the Poissonian statistics. This result allows us to determine with great accuracy the state filling condition of the quantum dots (QDs) and therefore to estimate the capture volume of the QDs. [ABSTRACT FROM AUTHOR]

We report strong heavy hole-light hole mixing in GaAs quantum dots grown by droplet epitaxy. Using the neutral and charged exciton emission as a monitor we observe the direct consequence of quantum dot symmetry reduction in this strain free system. By fitting the polar diagram of the emission with simple analytical expressions obtained from k·p theory we are able to extract the mixing that arises from the heavy-light hole coupling due to the geometrical asymmetry of the quantum dot. [ABSTRACT FROM AUTHOR]

We experimentally and theoretically investigate the photoluminescence broadening of different excitonic complexes in single self-assembled GaAs/AlGaAs quantum dots. We demonstrate that the excitonic fine-structure splitting leads to a sizable line broadening whenever the detection is not resolved in polarization. The residual broadening in polarized measurements is systematically larger for the exciton with respect to both the trion and the biexciton recombination. The experimental data agree with calculations of the quantum confined Stark effect induced by charge defects in the quantum dot (QD) environment, denoting the role of the QD spectator carrier rearrangement in reducing the perturbation of the fluctuating environment. [ABSTRACT FROM AUTHOR]

We observe single-photon interferograms for emission of a single self-assembled GaAs quantum dot. A phase stabilizer is applied to the interferometer, enabling us to trace autocorrelations of weak emissions with a photon-counting level. At low excitation, where the average number of excitons in a dot is less than one, interferography reveals a single exponential decay, reflecting excitonic decoherence. At moderately high excitation, polarization interference between the exciton-biexciton transitions is found to appear on the interferogram. The decoherence time and the binding energy of biexcitons are determined simultaneously. [ABSTRACT FROM AUTHOR]

In photoluminescence spectra of symmetric [111] grown GaAs/AlGaAs quantum dots in longitudinal magnetic fields applied along the growth axis, we observe in addition to the expected bright states also nominally dark transitions for both charged and neutral excitons. We uncover a strongly nonmonotonic, sign-changing field dependence of the bright neutral exciton splitting resulting from the interplay between exchange and Zeeman effects. Our theory shows quantitatively that these surprising experimental results are due to magnetic-field-induced ±3/2 heavy-hole mixing, an inherent property of systems with C3v point-group symmetry. [ABSTRACT FROM AUTHOR]

Abstract: We report on the power dependence of the exciton photoluminescence of single self-assembled GaAs/AlGaAs quantum dots. Interpreting the experimental data with the random population theory we demonstrate that the exciton states occupation probability can be described by Poissonian statistics, allowing to study the state filling condition and evaluate the QDs capture volume. In addition we study the effect of temperature on the QDs capture efficiency. [Copyright &y& Elsevier]

Abstract: We present the results of high resolution photoluminescence spectroscopy of single GaAs/AlGaAs quantum dots grown by droplet epitaxy technique. By measuring the line broadening and the linear polarization of the excitonic photoluminescence we get new insights on the role of extrinsic effects on the quantum dot symmetry. Taking advantage of the lack of strain in the GaAs/AlGaAs system we study the relationship between the geometrical elongation of the confining potential and the exciton fine structure splitting. [Copyright &y& Elsevier]