Three-wave diffraction in damaged epitaxial layers with a wurtzite structure
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- Kyutt, R.N. Tech. Phys. (2011) 56: 668. doi:10.1134/S1063784211050203
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Three-wave diffraction of X-rays is measured using the Renninger scheme for a series of GaN epitaxial layers of various thicknesses and degrees of structural perfection. In each 30°-angular interval of azimuthal rotation, all ten three-wave peaks determined by the geometry of diffraction with the 0001 first forbidden reflection and CuKα radiation are observed. The φ- and θ-scanned diffraction curves are measured for each three-wave combination. The angular FWHM of the diffraction peaks formed in experiments and its relation with the parameters of the two-wave diffraction pattern and the dislocation structure of the layers are analyzed. It is shown that the φ-scan peaks are less sensitive to the degree of structural perfection than the γ-mode peaks. The strongest dependence on the dislocation density for the latter peaks is observed for the \((1\bar 100)/(\bar 1101)\) and \((3\bar 2\bar 10)/(\bar 3211)\) three-wave combinations with a pure Laue component of secondary radiation, while the \((01\bar 13)/(0\bar 11\bar 2)\) combination with a large Bragg component exhibits the weakest dependence. Splitting of three-wave Renninger peaks associated with the coarse-block structure of some of the layers with rotations of the blocks about the normal to the surface is detected. The total integrated intensity of all three-wave combinations is determined and their ratios are in qualitative agreement with the theory.