InGaN Selfassembled Quantum Dots Investigated By X-Ray Diffraction-Anomalous-Fine Structure Technique

Piskorska, E.; Holý, V.; Siebert, Michael; Renevier, H.; Schmidt, Th.; Falta, J.; Yamaguchi, T.; Hommel, D.

doi:10.1063/1.2729779

Cited by 3 publications

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“…Diffuse scattering (due to strain fluctuations) and lateral peak broadening or satellite formation (due to in-plane spatial ordering) can typically be observed in RSMs taken from QD arrays. However, much of the work on QDs has been performed using high-intensity synchrotron radiation, using grazing-incidence small-angle x-ray scattering [211,212] and/or an x-ray diffraction anomalous fine structure [213,214] to find the strain distribution, composition variations and vertical and lateral correlations in a wide variety of QD samples [215,216]. Complex methods may be needed to extract the variation in both strain and composition across a QD [217].…”

Section: Quantum Dots (Qds)mentioning

confidence: 99%

X-ray diffraction of III-nitrides

2009

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The III-nitrides include the semiconductors AlN, GaN and InN, which have band gaps spanning the entire UV and visible ranges. Thin films of III-nitrides are used to make UV, violet, blue and green light-emitting diodes and lasers, as well as solar cells, high-electron mobility transistors (HEMTs) and other devices. However, the film growth process gives rise to unusually high strain and high defect densities, which can affect the device performance. X-ray diffraction is a popular, non-destructive technique used to characterize films and device structures, allowing improvements in device efficiencies to be made. It provides information on crystalline lattice parameters (from which strain and composition are determined), misorientation (from which defect types and densities may be deduced), crystallite size and microstrain, wafer bowing, residual stress, alloy ordering, phase separation (if present) along with film thicknesses and superlattice (quantum well) thicknesses, compositions and non-uniformities. These topics are reviewed, along with the basic principles of x-ray diffraction of thin films and areas of special current interest, such as analysis of non-polar, semipolar and cubic III-nitrides. A summary of useful values needed in calculations, including elastic constants and lattice parameters, is also given. Such topics are also likely to be relevant to other highly lattice-mismatched wurtzite-structure materials such as heteroepitaxial ZnO and ZnSe.

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Section: Quantum Dots (Qds)mentioning

confidence: 99%

X-ray diffraction of III-nitrides

2009

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“…1, show QDs with a density of 10 12 cm À2 , at an average height and diameter of 3.8 and 7.8 nm, respectively. The existence of QDs in the uncapped structure was also identified by grazing-incidence X-ray diffraction (Piskorska et al, 2007).…”

Section: Methodsmentioning

confidence: 99%

Local structure of uncapped and capped InGaN/GaN quantum dots

Piskorska‐Hommel

Schmidt

Siebert

et al. 2009

J Synchrotron Radiat

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The local structure around the indium atoms in uncapped and capped In(x)Ga(1-x)N quantum dots has been studied by In K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy. The samples were grown by metal organic vapour phase epitaxy. The EXAFS was successfully applied to study the structural properties of buried quantum dots which are not optically active. The analysis revealed that capping the quantum dots with GaN does not affect the bond distances of the In-N and In-Ga, but makes the In-In distance shorter by 0.04 A.

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Gallium clustering and structural effects of hydrogenation in InGaN/GaN nanostructures

Ciatto

Pettinari

Polimeni

2018

Journal of Applied Physics

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We addressed the issue of atomic ordering in a series of In-rich InxGa1−xN epilayers grown on a GaN/AlN/sapphire(0001) epitaxial template by quantitatively measuring the Ga-cation coordination in the second atomic shell of Ga. We used Diffraction Anomalous Fine Structure Spectroscopy (DAFS) at the Ga K-edge to select the signal coming from the Ga atoms in the epilayer and eliminate any contribution from the buffer layer. DAFS measurements were also performed on hydrogenated epilayers in order to investigate the possible formation of Ga-H complexes. We find that deviation from cation random distribution in the form of Ga clustering is present in both untreated and hydrogenated samples and that in the latter ones the second atomic shell around Ga is modified, suggesting an additional perturbation of the cation sublattice related to hydrogen. However, comparing the present results with In K-edge x-ray absorption spectra previously reported, we conclude that the formation of Ga-H complexes vs. In-H ones is unlikely. Cation clustering has to be anyway taken into account as a possible channel playing in the determination of the optical bandgap of these technology-oriented semiconductors.

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InGaN Selfassembled Quantum Dots Investigated By X-Ray Diffraction-Anomalous-Fine Structure Technique

Cited by 3 publications

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X-ray diffraction of III-nitrides

X-ray diffraction of III-nitrides

Local structure of uncapped and capped InGaN/GaN quantum dots

Gallium clustering and structural effects of hydrogenation in InGaN/GaN nanostructures

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