The effect of Si doping (3 x 1018/cm3) upon the crystalline quality of GaN epitaxial layers grown onto the sapphire c-face was studied by means of high-resolution X-ray diffraction; including several Bragg reflections in various scanning directions, reciprocal space maps, radial scans, and measurements of radii of curvature. Elastic and hydrostatic strain components were deduced by taking account of strains introduced into the sapphire substrate by the highly mismatched GaN layer. The Si-doped and undoped GaN layers were grown using an atmospheric-pressure metalorganic chemical vapour deposition technique. All of the layers were under compression, but with slightly higher stresses existing in the undoped layer. The hydrostatic strain component remained unchanged. It was found that the doping of GaN with Si decreased the edge-dislocation density and increased the screw dislocation density. It was concluded that edge-type threading dislocation arrangements, piled up in small-angle columnar grain boundaries, predominated in both types of sample.

High-Resolution X-Ray Diffraction Defect Structure Characterization in Si-Doped and Undoped GaN Films. E.Zielińska-Rohozińska, M.Regulska, V.S.Harutyunyan, K.Pakuła, J.Borowski: Materials Science and Engineering B, 2002, 91-92, 441-4