Grazing-incidence diffraction anomalous fine structure: Application to the structural investigation of group-III nitride quantum dots

Journal Article · Fri Jun 15 04:00:00 EDT 2007 · Physical Review. B, Condensed Matter and Materials Physics

DOI:https://doi.org/10.1103/PHYSREVB.75.235312· OSTI ID:20951544

Coraux, J; Favre-Nicolin, V; Renevier, H ^[1]; Proietti, M G ^[2]; Daudin, B ^[1]

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1. Departement de Recherche Fondamentale sur la Matiere Condensee, Commissariat a l'Energie Atomique, SP2M/NRS, 17 rue des Martyrs, 38054 Grenoble Cedex 9 (France)
2. Departamento de Fisica de la Materia Condensada, Instituto de Ciencia de Materiales de Aragon, CSIC-Universidad de Zaragoza, c. Pedro Cerbuna 12, 50009 Zaragoza (Spain)

The relevance of grazing-incidence anomalous diffraction as a tool to investigate the strain and structure of small-size embedded nano-objects is examined. Multiple scattering effects, originating from the grazing-incidence setup, are analyzed with a special emphasis on the cusp of the diffraction anomalous spectrum and the extended diffraction anomalous fine-structure oscillations. It is shown that even for grazing-incidence angle, a Born approximation treatment is justified for quantum dots (QDs) on top of a thin wetting layer. The discussion focuses on the overgrowth of AlN on top of GaN QDs. Both the in-plane and out-of-plane strains in the dots can be specifically determined, by extracting the Ga partial scattering amplitude from measurements of the scattered intensity along both the in- and out-of-plane directions, close to the (3030) and (3032) reflections, at several energies across the Ga K edge. The study is complemented by the analysis of the local environment of Ga atoms in the dots through the measurement of the fine-structure oscillations in diffraction condition. The oscillations are found almost insensitive to the grazing-incidence multiple-scattering effects. Accordingly, the out-of-plane strain and possible intermixing specifically in the dots can be deduced. The QDs are shown to remain pure GaN all along the capping process. The QDs strain state exhibits a larger strain relaxation than expected from an elastic model, suggesting the presence of a plastic strain relaxation, possibly through dislocations at the vicinity of the QDs. Finally, the influence of the substrate as regards strain relaxation in the QDs is discussed by comparing our results to those we previously obtained for a series of samples grown on AlN/sapphire.

• OSTI ID: 20951544
• Journal Information: Physical Review. B, Condensed Matter and Materials Physics, Journal Name: Physical Review. B, Condensed Matter and Materials Physics Journal Issue: 23 Vol. 75; ISSN 1098-0121
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM NITRIDES
BORN APPROXIMATION
CUSPED GEOMETRIES
DISLOCATIONS
FINE STRUCTURE
GALLIUM NITRIDES
INCIDENCE ANGLE
LAYERS
MULTIPLE SCATTERING
OSCILLATIONS
PLASTICITY
QUANTUM DOTS
RELAXATION
SAPPHIRE
SCATTERING AMPLITUDES
SEMICONDUCTOR MATERIALS
STRAINS
X-RAY DIFFRACTION