Spectra of dark and bright excitons in alloyed nanowire quantum dots

Zieliński, Michał

doi:10.1103/physrevb.100.045309

Cited by 9 publications

(12 citation statements)

References 83 publications

(110 reference statements)

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“…In contrary, hole levels (Fig. 2 e–h) are strongly affected by alloying what appears to be a general feature of InAs/InP nanostructures 62 , 69 , 74 likely due to smaller inter-level spacing of hole states, as compared to electrons. As a result, energies of excited hole states for alloyed systems (in particular for and ) are dominated by alloy randomness, with a weak dependence on anisotropy.…”

Section: Resultsmentioning

confidence: 93%

“…We note however here, that more extensive studies on role of alloying (especially for large t values) need the be performed, e.g. by considering more than a single sample corresponding to the same average composition 68,69 . Due to large number of atoms, and related computational complexity of the configuration interaction these are ongoing studies, and their results will be presented elsewhere.…”

Section: Resultsmentioning

confidence: 99%

“…Hence, based on group-theoretical reasoning and contrary to simplified arguments shape deformation can in fact lead to a vanishing fine structure splitting. The pictures gets more complicated for alloyed systems with polarization axes getting randomized 69,82 . However, for larger t values the bright exciton polarizations still maintain their dominant components in the [ 110]/ [110] basis, therefore we present these components on Fig.…”

Section: Resultsmentioning

confidence: 99%

“…The pictures gets more complicated for alloyed systems with polarization axes getting randomized 69 , 82 . However, for larger t values the bright exciton polarizations still maintain their dominant components in the [ ]/[110] basis, therefore we present these components on Fig.…”

Section: Resultsmentioning

confidence: 99%

“…No self-assembled quantum dash (or quantum dot) can be grown without the mixing of nanostructure material with the material of the surrounding matrix. This composition mixing, or alloying, leads to related alloy randomness, which usually affects the bright exciton spectra in a profound way 68 , 69 . In this work, we show that for a relatively small ( or 20%) amount of phosphorous migrating into the InAs quantum dash from the surrounding InP matrix is it still possible to observe the reduction of the BES for elongation aspect ratio values between 6 and 8.…”

Section: Introductionmentioning

confidence: 99%

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Vanishing fine structure splitting in highly asymmetric InAs/InP quantum dots without wetting layer

Zieliński

2020

Sci Rep

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Contrary to simplified theoretical models, atomistic calculations presented here reveal that sufficiently large in-plane shape elongation of quantum dots can not only decrease, but even reverse the splitting of the two lowest optically active excitonic states. Such a surprising cancellation of bright-exciton splitting occurs for shape-anisotropic nanostructures with realistic elongation ratios, yet without a wetting layer, which plays here a vital role. However, this non-trivial effect due to shapeelongation is strongly diminished by alloy randomness resulting from intermixing of InAs quantumdot material with the surrounding InP matrix. Alloying randomizes, and to some degree flattens the shape dependence of fine-structure splitting giving a practical justification for the application of simplified theories. Finally, we find that the dark-exciton spectra are rather weakly affected by alloying and are dominated by the effects of lateral elongation. Quantum dots 1,2 are man-made semiconductor nanostructures that come in a wide variety of types 3-5 , and are extensively studied with interest driven by both basic scientific curiosity as well as promising applications in quantum information 6 , computing 7,8 , and cryptography 9. Apart from the elementary excitations, electrons and holes, quantum dots can confine interacting electron-hole pairs, namely excitons. 10 An emission cascade from a two exciton (biexciton) state, through two indistinguishable exciton states should lead to the emission of polarization entangled photon pairs. 9,11-13 However, in realistic quantum dots the intermediate exciton state is often split by the electron-hole exchange interaction 14-16 hindering the efficiency of the entanglement generation. This energetic difference between the two bright exciton states, known as the fine-structure splitting or the bright exciton splitting (BES) is typically (10-100 µeV) much larger than the emission linewidth (∼ 1 µeV). Tailoring the BES in nanostructures is thus essential due to its relevance for photon entanglement generation. 7,11,17,18 This is particularly important for InAs/InP nanostructures, which are promising candidates for quantum emitters at 1.3 or 1.55 µm telecommunication relevant wavelengths 19-22. Notably, InAs/InP nanostructures can be fabricated in various ways, including self-assembled and nanowire quantum dots 23-27 of quasi-cylindrical shapes, as well as strongly elongated dots 28-42 , sometimes referred to as quantum dashes. Similarly to cylindrically-shaped dot systems, quantum dashes have the potential for applications 30,31,43-45 combined with considerable tuning capabilities 46,47. The manipulation of the BES aimed towards generation of entangled photon pairs is a vital and broad research area with significant efforts have been made utilizing post-growth annealing 48,49 , spectral filtering 9 , sample selection 50,51 , growth of highly symmetric structures 24,26,52-54 , and the application of external electric 55,56 , magnetic 18,57,58 , and strain fields 59-61. With respect t...

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Section: Resultsmentioning

confidence: 93%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Vanishing fine structure splitting in highly asymmetric InAs/InP quantum dots without wetting layer

Zieliński

2020

Sci Rep

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Empirical tight-binding parameters for wurtzite group III–V(non-nitride) and IV materials

Sink

Pryor

2023

AIP Advances

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Suitable tight-binding models for wurtzite III–V (non-nitride) and group-V materials are presently missing in the literature. Many commonly used nearest neighbor tight-binding models for cubic-zincblende semiconductors result in highly inaccurate band structures when transferred to hexagonal polytypes. Wurtzite parameters would be of use in modeling nanowires that primarily condense into either wurtzite or zincblende crystal phases. Nanowire growth has seen significant development over the last decade, and polytypic heterostructures are now able to be fabricated. We have produced a set of spds* tight-binding parameters to be used in the hexagonal-wurtzite crystal phase for non-nitride III–V and group V semiconductors. We confine our parameter space to remain in the vicinity of a well-established zincblende parameter set to ensure semi-transferability between the wurtzite and zincblende polytypes. Our wurtzite parameters, when combined with the existing zincblende parameters, enable modeling electronic structures of heterostructures containing both the wurtzite and zincblende crystal phases.

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Electric field tuning of excitonic fine-structure splitting in asymmetric InAs/InP nanowire quantum dot molecules

Świderski

Zieliński

2019

Phys. Rev. B

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Spectra of dark and bright excitons in alloyed nanowire quantum dots

Cited by 9 publications

References 83 publications

Vanishing fine structure splitting in highly asymmetric InAs/InP quantum dots without wetting layer

Vanishing fine structure splitting in highly asymmetric InAs/InP quantum dots without wetting layer

Empirical tight-binding parameters for wurtzite group III–V(non-nitride) and IV materials

Electric field tuning of excitonic fine-structure splitting in asymmetric InAs/InP nanowire quantum dot molecules

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