Growth optimization for high quality GaN films grown by metal-organic chemical vapor deposition

Abstract

ABSTRACTGaN layers were grown on c-plane sapphire substrates by using a conventional two step growth method via metal organic chemical vapor deposition (MOCVD). The effect of different growth conditions used in the deposition of the low temperature nucleation layer and high temperature islands on the crystalline quality of the GaN layers was investigated by high resolution X-ray diffraction (HRXRD) and transmission electron microscopy (TEM). The polar (tilt) and azimuthal (twist) spread were estimated from the full width at half maximum (FWHM) values of the omega rocking curves (¥ø-RCs) recorded from the planes parallel and perpendicular to the sample surface. It was found from the XRD and TEM study that the edge and mixed type threading dislocations are dominant defects so that the relevant figure of merit (FOM) for the crystalline quality should be considered only by the FWHM value of ¥ø-RC of the surface perpendicular plane. The result showed that the mixed- and edge-types dislocations were strongly associated with the growth conditions used in the deposition of the nucleation layer and high temperature islands.