Direct, Independent Measurement of Twist and Tilt Mosaic as a Function of Thickness in Epitaxial GaN

Abstract

The twist and tilt mosaics in a series of GaN epitaxial films grown by metal-organic vapour-phase epitaxy (MOVPE) have been measured directly by grazing incidence in-plane X-ray diffraction and in the standard symmetric high resolution setting. The variation in tilt mosaic with layer thickness fits well the model of Ayers. A similarly good fit to the same function for the twist mosaic dependence on epilayer thickness is found, indicating that the ratio of edge to screw dislocations remains constant for all films.