Wing tilt investigations on GaN epilayer grown on maskless grooved sapphire by MOCVD

GaN epilayer is grown on maskless periodically grooved sapphire by metal organic chemical vapor deposition (MOCVD) in this article. Wing tilt is detected by high resolution X-ray rocking curve. Inhomogeneous deformations between the wing and mesa regions are found by atomic force microscopy (AFM) characterization. The stress distribution is investigated using finite-element simulations. Inhomogeneous stress distribution in the mesa and wing regions is shown, which is also confirmed by micro-Raman spectroscopy. The results show that the wing tilt in GaN layers grown on maskless periodically grooved sapphire mainly originates from the different deformations for mesa and wing region caused by inhomogeneous stress distribution.