X‐ray diffraction study of strain and defect structure of nonpolar a‐plane GaN‐layers grown on r‐plane sapphire

Structural state of nonpolar a‐plane GaN layers grown by MOVPE on r‐plane sapphire is investigated by X‐ray diffraction method. Interplanar spacings were measured in three directions and corresponding strains were determined. A crystalline perfection was studied by measurement of diffraction peaks of θ‐ and θ–2θ‐scanning in Bragg‐ and Laue‐diffraction geometry. Their FWHM was analyzed by Williamson–Hall plots. Anisotropy of the elastic strains and the peak broadening was revealed. It is shown that a different broadening of diffraction pattern in two in‐plane directions is not caused by mosaicity and can be explained by a specific distribution of dislocations.