The influence of nitridation time on the structural properties of GaN grown on Si (111) substrate

In the present paper, the effect of in-situ substrate nitridation time on crystalline quality of GaN films grown on Si (111) substrates by metal organic chemical vapor deposition (MOCVD) were investigated. A thin buffer layer of silicon nitride (SiNx) with various thicknesses was achieved through the nitridation of substrate at different nitiridation times ranging from 0 to 660 s. The structural characteristics, such as dislocation densities, correlation lengths of columnar crystallites, the tilt and twist of the mosaic structure, and the angles of rotational disorder, were all studied in detail by using a planar and cross-sectional view of high resolution transmission electron microscopy (HRTEM) and X-ray diffraction (HRXRD) performed at different scattering geometries. It was found that the dislocation densities, lateral coherence lengths, vertical coherence lengths, and the tilt and twist of mosaic blocks in GaN films monotonically varies with the nitridation time. The experimental findings showed that the nitridation times had more influence on edge dislocation densities than the screw type.