title: Three-wave X-ray diffraction in distorted epitaxial structures.
abstract: Three-wave diffraction has been measured for a set of GaN, AlN, AlGaN and ZnO epitaxial layers grown onc-sapphire. A Renninger scan for the primary forbidden 0001 reflection was used. For each of the three-wave combinations, θ-scan curves were measured. The intensity and angular width of both ϕ- and θ-scan three-wave peaks were analyzed. The experimental data were used to determine properties of the multiple diffraction pattern in highly distorted layers. It is shown that the FWHM of θ scans is highly sensitive to the structural perfection and strongly depends on the type of three-wave combination. The narrowest peaks are observed for multiple combinations with the largestlindex of the secondaryhklreflection. An influence of the type of the dislocation structure on the θ-scan broadening was revealed. These experimental facts are interpreted by considering the scanning geometry in the reciprocal space and taking into account the disc-shaped reciprocal-lattice points. The total integrated intensities of all the three-wave combinations were determined and their ratios were found to be in only a qualitative agreement with the theory. For AlGaN layers, the presence of the nonzero 0001 reflection was revealed, in contrast to AlN and GaN films.
authors.affiliation: Ioffe Physical Technical Institute, Russian Academy of Sciences, St Petersburg, Russian Federation.
authors.forename: Reginald
authors.initials: R
authors.lastname: Kyutt
authors.forename: Mikhail
authors.initials: M
authors.lastname: Scheglov
keywords: X-ray diffraction; epitaxial layers; multiple diffraction; structural defects; wurtzite structure
references.citation: Acta Crystallogr A. 2002 Sep;58(Pt 5):473-86
references.pmid: 12192121
references.citation: Acta Crystallogr A. 2007 May;63(Pt 3):251-6
references.pmid: 17435289