Determination of the azimuthal orientational spread of GaN films by x-ray diffraction

Abstract

We present a simple but reliable method to determine the azimuthal orientational spread of imperfect epitaxial layers by x-ray diffraction. This method requires the measurement of ω-scans in skew geometry from reflections with increasing lattice plane inclination φ, and a fit of the data by a geometrical model that considers the simultaneous presence of polar and azimuthal orientational spread within the layer. The values thus obtained for various GaN layers grown on SiC are shown to be in good agreement with those measured directly by φ-scans of the (11̄00) reflection in grazing incidence, and with those deduced from the edge dislocation densities determined by plan-view transmission electron microscopy.

High optical and structural quality of GaN epilayers grown on (2¯01) β-Ga2O3

“…In particular, the (0002) RCs are broadened by mosaic tilt caused by screwtype and mixed dislocations (as well as the lateral coherence length), while the (10 15) reflection is also sensitive to edgetype dislocations (causing twist) when measured with the skew symmetric geometry. 21 The two samples show very similar behavior with only slightly higher values for the sample grown on Ga 2 O 3 suggesting slightly higher dislocation densities, an impressive result for initial growth experiments with little optimization of growth parameters. The mosaicity was further studied by using the RSM of the (10 15) asymmetric reflection as shown in Figs.…”

X-ray diffraction peak profiles from threading dislocations in GaN epitaxial films

“…All asymmetric rocking curves were recorded in skew geometry. 5 We denote the GaN reflections in the form hk.l which is equivalent to the four-index notation hkil for hexagonal crystals with h + k + i = 0.…”

“…2,3,4, 5,6 This designation stems from the model of misoriented blocks 6 which is not appropriate for strains caused by randomly distributed dislocations. In this case, the description in terms of meansquared distortions 7 is actually more adequate.…”

Defect formation in GaN grown on vicinal 4H‐SiC (0001) substrates

“…To have access to this information, it is useful to perform ω-scans of a-symmetrical reflections. The full width at half maximum (FWHM) does not directly correspond to the twist [20], but a comparison between the samples is a good indication of their quality. X-ray rocking curve measurements on these samples, which were previously reported [10], showed that the structural quality of the GaN epilayer is worse for larger miscut angles.…”