Electron tomography of (In,Ga)N insertions in GaN nanocolumns grown on semi-polar (112̄2) GaN templates

Niehle, Michael; Trampert, A.; Albert, Steven; Bengoechea-Encabo, Ana; Calleja, E.

doi:10.1063/1.4914102

Cited by 3 publications

(3 citation statements)

References 16 publications

(18 reference statements)

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“…23 Atomic force micrographs of uncapped QDs are of limited relevance for this purpose, as significant in-and out-of-plane In segregation may occur during the QD overgrowth by GaAs. 24 The three-dimensional shape of a single embedded QD can be reconstructed by atom probe 24 or electron tomography, 25,26 but it is difficult to achieve results of statistical significance with these techniques. Magneto-PL is an alternative technique to obtain an estimate of the size of embedded InAs QDs or, rather, the spatial extent of the confining potential.…”

Section: Resultsmentioning

confidence: 99%

Fine structure of excitons in InAs quantum dots on GaAs(110) planar layers and nanowire facets

et al. 2017

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We investigate the optical properties of InAs quantum dots grown by molecular beam epitaxy on GaAs(110) using Bi as a surfactant. The quantum dots are synthesized on planar GaAs(110) substrates as well as on the {110} sidewall facets of GaAs nanowires. At 10 K, neutral excitons confined in these quantum dots give rise to photoluminescence lines between 1.1 and 1.4 eV. Magneto-photoluminescence spectroscopy reveals that for small quantum dots emitting between 1.3 and 1.4 eV, the electron-hole coherence length in and perpendicular to the (110) plane is on the order of 5 and 2 nm, respectively. The quantum dot photoluminescence is linearly polarized, and both binding and antibinding biexcitons are observed, two findings that we associate with the strain in the (110) plane This strain leads to piezoelectric fields and to a strong mixing between heavy and light hole states, and offers the possibility to tune the degree of linear polarization of the exciton photoluminescence as well as the sign of the binding energy of biexcitons. arXiv:1704.08543v1 [cond-mat.mes-hall]

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Section: Resultsmentioning

confidence: 99%

Fine structure of excitons in InAs quantum dots on GaAs(110) planar layers and nanowire facets

et al. 2017

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“…The transmission electron microscope (TEM) is a frequently used and powerful tool to obtain information about the structure and chemical composition of such nanostructures on the atomic scale [9]. However, the lower symmetry of these 3D nanostructures compared to, for example, planar systems makes the interpretation of TEM micrographs far more difficult.…”

Section: Introductionmentioning

confidence: 99%

“…This enables new and advanced possibilities to describe and analyze the morphology and chemical composition of complex structures like core-shell NWs. So far, only a few publications have been published concerning electron tomography on NW structures [9–15] or embedded QD structures [16].…”

Section: Introductionmentioning

confidence: 99%

Electron Tomography of Pencil-Shaped GaN/(In,Ga)N Core-Shell Nanowires

et al. 2019

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The three-dimensional structure of GaN/(In,Ga)N core-shell nanowires with multi-faceted pencil-shaped apex is analyzed by electron tomography using high-angle annular dark-field mode in a scanning transmission electron microscope. Selective area growth on GaN-on-sapphire templates using a patterned mask is performed by molecular beam epitaxy to obtain ordered arrays of uniform nanowires. Our results of the tomographic reconstruction allow the detailed determination of the complex morphology of the inner (In,Ga)N multi-faceted shell structure and its deviation from the perfect hexagonal symmetry. The tomogram unambiguously identifies a dot-in-a-wire configuration at the nanowire apex including the exact shape and size, as well as the spatial distribution of its chemical composition. Electronic supplementary material The online version of this article (10.1186/s11671-019-3072-1) contains supplementary material, which is available to authorized users.

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Structure and Composition of Isolated Core-Shell(In,Ga)N/GaNRods Based on Nanofocus X-Ray Diffraction and Scanning Transmission Electron Microscopy

et al. 2017

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Nanofocus x-ray diffraction is used to investigate the structure and local strain field of an isolated ðIn; GaÞN=GaN core-shell microrod. Because the high spatial resolution of the x-ray beam is only 80 × 90 nm 2 , we are able to investigate several distinct volumes on one individual side facet. Here, we find a drastic increase in thickness of the outer GaN shell along the rod height. Additionally, we performed highangle annular dark-field scanning-transmission-electron-microscopy measurements on several rods from the same sample showing that (In,Ga)N double-quantum-well and GaN barrier thicknesses also increase strongly along the height. Moreover, plastic relaxation is observed in the top part of the rod. Based on the experimentally obtained structural parameters, we simulate the strain-induced deformation using the finiteelement method, which serves as the input for subsequent kinematic scattering simulations. The simulations reveal a significant increase of elastic in-plane relaxation along the rod height. However, at a certain height, the occurrence of plastic relaxation yields a decrease of the elastic strain. Because of the experimentally obtained structural input for the finite-element simulations, we can exclude unknown structural influences on the strain distribution, and we are able to translate the elastic relaxation into an indium concentration which increases by a factor of 4 from the bottom to the height where plastic relaxation occurs.

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Electron tomography of (In,Ga)N insertions in GaN nanocolumns grown on semi-polar (112̄2) GaN templates

Cited by 3 publications

References 16 publications

Fine structure of excitons in InAs quantum dots on GaAs(110) planar layers and nanowire facets

Fine structure of excitons in InAs quantum dots on GaAs(110) planar layers and nanowire facets

Electron Tomography of Pencil-Shaped GaN/(In,Ga)N Core-Shell Nanowires

Structure and Composition of Isolated Core-Shell(In,Ga)N/GaNRods Based on Nanofocus X-Ray Diffraction and Scanning Transmission Electron Microscopy

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