High–temperature droplet epitaxy of symmetric GaAs/AlGaAs quantum dots

Bietti, Sergio; Basset, Francesco Basso; Tuktamyshev, Artur; Bonera, Emiliano; Fedorov, Alexey; Sanguinetti, S.

doi:10.1038/s41598-020-62248-9

Cited by 25 publications

(23 citation statements)

References 48 publications

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“…In other QDs we measured values between 30 and 140

eV (not shown). These values are very large if compared with QDs grown on (111) substrates, where the three-fold symmetry of the crystal provides a more isotropic surface diffusion and a corresponding triangular or hexagonal nanostructure shape [ 26 , 27 , 35 , 36 , 41 , 42 , 46 , 61 , 68 , 69 , 70 , 71 ]. The origin of this splitting in (311)A QDs is attributed to asymmetries in the QDs shape that is affected by the anisotropy of the underlying crystal.…”

Section: Resultsmentioning

confidence: 99%

“…Another aspect relevant for applications is the possibility to grow high-quality nanostructures on different substrate orientation, providing the ground for highly symmetric QDs on (111)A surfaces [ 26 , 27 , 35 , 36 , 41 , 42 , 46 , 61 , 68 , 69 , 70 , 71 ] (e.g., for entangled photon pairs generation) and for ultra-high density quantum wires [ 60 ] and QDs [ 19 , 32 , 38 , 63 , 64 , 65 , 72 , 73 ] formation on the highly anisotropic (311)A surface (e.g., for laser emission). This latter class of nanostructures grown on (311)A surface has not yet been thoroughly investigated and a clear assessment of the corresponding excitonic dynamics has not yet been reported.…”

Section: Introductionmentioning

confidence: 99%

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Exciton Dynamics in Droplet Epitaxial Quantum Dots Grown on (311)A-Oriented Substrates

et al. 2020

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Droplet epitaxy allows the efficient fabrication of a plethora of 3D, III–V-based nanostructures on different crystalline orientations. Quantum dots grown on a (311)A-oriented surface are obtained with record surface density, with or without a wetting layer. These are appealing features for quantum dot lasing, thanks to the large density of quantum emitters and a truly 3D lateral confinement. However, the intimate photophysics of this class of nanostructures has not yet been investigated. Here, we address the main optical and electronic properties of s-shell excitons in individual quantum dots grown on (311)A substrates with photoluminescence spectroscopy experiments. We show the presence of neutral exciton and biexciton as well as positive and negative charged excitons. We investigate the origins of spectral broadening, identifying them in spectral diffusion at low temperature and phonon interaction at higher temperature, the presence of fine interactions between electron and hole spin, and a relevant heavy-hole/light-hole mixing. We interpret the level filling with a simple Poissonian model reproducing the power excitation dependence of the s-shell excitons. These results are relevant for the further improvement of this class of quantum emitters and their exploitation as single-photon sources for low-density samples as well as for efficient lasers for high-density samples.

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“…In other QDs we measured values between 30 and 140

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Exciton Dynamics in Droplet Epitaxial Quantum Dots Grown on (311)A-Oriented Substrates

et al. 2020

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“…The elongation of QD shape is a natural consequence of the SK growth technique. Various techniques can be used to obtain QDs with small FSS such as, growing QDs on (111) surfaces in which the underlying C

crystal symmetry assists in obtaining uniform QDs [ 107 , 108 , 109 , 110 , 111 ]. Fabrication of QDs in locally etched pits is another technique to reduce anisotropy in QDs size and shape [ 112 ].…”

Section: Strained Inas/inp Deqdsmentioning

confidence: 99%

Atomic-Scale Characterization of Droplet Epitaxy Quantum Dots

Gajjela

Koenraad

2021

Nanomaterials

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The fundamental understanding of quantum dot (QD) growth mechanism is essential to improve QD based optoelectronic devices. The size, shape, composition, and density of the QDs strongly influence the optoelectronic properties of the QDs. In this article, we present a detailed review on atomic-scale characterization of droplet epitaxy quantum dots by cross-sectional scanning tunneling microscopy (X-STM) and atom probe tomography (APT). We will discuss both strain-free GaAs/AlGaAs QDs and strained InAs/InP QDs grown by droplet epitaxy. The effects of various growth conditions on morphology and composition are presented. The efficiency of methods such as flushing technique is shown by comparing with conventional droplet epitaxy QDs to further gain control over QD height. A detailed characterization of etch pits in both QD systems is provided by X-STM and APT. This review presents an overview of detailed structural and compositional analysis that have assisted in improving the fabrication of QD based optoelectronic devices grown by droplet epitaxy.

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“…An appealing possibility offered by DE is the growth of nanostructures on different substrate orientations: in addition to the conventional (001), QDs can be grown on the three-fold symmetric (111)A surface [25,26,49,56,[58][59][60][61][62][63][64][65] (e.g., for the fabrication of sources of entangled photons) and on the highly anisotropic (311)A surface [17,34,47,[50][51][52][66][67][68][69] (e.g., to obtain large QDs density for laser emission). These substrate orientations affect the QDs properties and, in turn, their photophysics by modifying the confining potential (e.g., symmetry) for electrons and holes, and are thus a key tool for engineering the exciton dynamics and the corresponding optical properties.…”

Section: Introductionmentioning

confidence: 99%

Polarization Anisotropies in Strain-Free, Asymmetric, and Symmetric Quantum Dots Grown by Droplet Epitaxy

et al. 2021

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We provide an extensive and systematic investigation of exciton dynamics in droplet epitaxial quantum dots comparing the cases of (311)A, (001), and (111)A surfaces. Despite a similar s-shell exciton structure common to the three cases, the absence of a wetting layer for (311)A and (111)A samples leads to a larger carrier confinement compared to (001), where a wetting layer is present. This leads to a more pronounced dependence of the binding energies of s-shell excitons on the quantum dot size and to the strong anti-binding character of the positive-charged exciton for smaller quantum dots. In-plane geometrical anisotropies of (311)A and (001) quantum dots lead to a large electron-hole fine interaction (fine structure splitting (FSS) ∼100 μeV), whereas for the three-fold symmetric (111)A counterpart, this figure of merit is reduced by about one order of magnitude. In all these cases, we do not observe any size dependence of the fine structure splitting. Heavy-hole/light-hole mixing is present in all the studied cases, leading to a broad spread of linear polarization anisotropy (from 0 up to about 50%) irrespective of surface orientation (symmetry of the confinement), fine structure splitting, and nanostructure size. These results are important for the further development of ideal single and entangled photon sources based on semiconductor quantum dots.

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High–temperature droplet epitaxy of symmetric GaAs/AlGaAs quantum dots

Cited by 25 publications

References 48 publications

Exciton Dynamics in Droplet Epitaxial Quantum Dots Grown on (311)A-Oriented Substrates

Exciton Dynamics in Droplet Epitaxial Quantum Dots Grown on (311)A-Oriented Substrates

Atomic-Scale Characterization of Droplet Epitaxy Quantum Dots

Polarization Anisotropies in Strain-Free, Asymmetric, and Symmetric Quantum Dots Grown by Droplet Epitaxy

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