X-Ray Diffraction Analysis of Features of the Crystal Structure of GaN/[Al.sub.0.32][Ga.sub.0.68]N HEMT-Heterostructures by the Williamson--Hall Method

The fitting of 0/20 and ra peaks in X-ray diffraction curves is shown to be most accurate in the case of using an inverse fourth-degree polynomial or probability density function with Student's distribution (Pearson type VII function). These functions describe well both the highest- intensity central part of the experimental peak and its low-intensity broadened base caused by X-ray diffuse scattering. The mean microdeformation [epsilon] and mean vertical domain size D are determined by the Williamson-Hall method for layers of GaN ([epsilon] [approximately equal to] 0.00006, D [approximately equal to] 200 nm) and [Al.sub.0.32][Ga.sub.0.68]N ([epsilon] = 0.0032 [+ or -] 0.0005, D = 24 [+ or -] 7 nm). The D value obtained for the [Al.sub.0.32][Ga.sub.0.68]N layer is most likely to result from the nominal thickness of this layer, which is 11 nm. DOI: 10.1134/S1063782618060209