Crystal Tilts in Epitaxially Laterally Overgrown GaN FilmsDetermined by Four-Circle X-Ray Diffraction

Crystal tilts in epitaxially laterally overgrown (ELO) GaN films via hydride vapor phase epitaxy (HVPE) on sapphire substrates have been investigated by using four-circle x-ray diffraction method. Three diffraction peaks corresponding to the (0002) reflection of vertically epitaxial and tilted GaN domains are observable in the x-ray rocking curve. The angle separations Δω between the main peak and two lobes change with the azimuth angle Ф. The dependence of Δω on Ф and the crystal tilt angle θ has been calculated based on the standard kinetic x-ray diffraction model. The crystal tilt angle of a typical HVPE ELO GaN sample has been determined to be 2.379°C.