Tilt of InGaN layers on miscut GaN substrates

We report on the crystallographic orientation of InGaN layers grown on GaN substrates with a miscut with respect to c-planes up to 2.5 degrees. The samples were examined using high-resolution X-ray diffraction (HRXRD) and atomic force microscopy (AFM). Because of the large.(up to about 2% in this study) lattice mismatch between InGaN and GaN, an additional tilt between the c lattice plans of InGaN and GaN was observed and explained by using the Nagai model [J. Appl] Phys. 45, 3789 (1974)]. We observed that for part of the samples, this tilt is about 10% smaller compared to the one predicted by the model. The experimental data are important for understanding the microstructuure of InGaN layers grown on substrates of non-perfect morphology.