X-Ray Diffraction Analysis of Features of the Crystal Structure of GaN/Al_0.32Ga_0.68N HEMT-Heterostructures by the Williamson–Hall Method

Abstract

The fitting of θ/2θ and ω 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 ε and mean vertical domain size D are determined by the Williamson–Hall method for layers of GaN (ε ≈ 0.00006, D ≈ 200 nm) and Al_0.32Ga_0.68N (ε = 0.0032 ± 0.0005, D = 24 ± 7 nm). The D value obtained for the Al_0.32Ga_0.68N layer is most likely to result from the nominal thickness of this layer, which is 11 nm.