Inhomogeneous strain in GaN nanowires determined from x-ray diffraction peak profiles

High-resolution x-ray diffraction peak profiles from self-induced GaN nanowires are studied theoretically and experimentally. We show that the peak profiles can be explained as a result of an inhomogeneous fluctuating strain in nanowires. We attribute this strain to random distortions caused by lattice defects at the interface between the nanowire and the substrate and at coalescence joints. An exponential decay of the mean-squared strain along the nanowire describes the peak profiles in successive diffraction orders.