The methods of 2- and 3-crystal X-ray diffractometry were used to study the dislocation structures of thick layers which had been grown, via chloride gaseous-phase epitaxy, onto sapphire as well as onto a thin GaN layer which had been grown by using the metal-organic synthesis method. Five components of the micro-distortion tensor, and the sizes of the coherent scattering regions along the sample surface and along the normal to it, were deduced from measurements of the diffracted intensity in the Bragg and Laue geometries. These quantities were used to analyse the type and geometry of the dislocations present, and to calculate the number densities of the main types of dislocation. The density of the vertical screw dislocations, as well as of the edge dislocations, decreased (by a factor of 1.5 to 3) during growth onto a thin GaN layer. The diffraction parameters of thick layers grown onto metal-organic synthesized GaN substrates suggested that they had a monocrystalline structure.

X-Ray Measurement of a Micro-Distortion Tensor and its Application in an Analysis of the Dislocation Structure of Thick GaN Layers Obtained by Hydrochloride Gaseous-Phase Epitaxy. V.V.Ratnikov, R.N.Kyutt, T.V.Shubina: Fizika Tverdogo Tela, 2000, 42[12], 2140-6 (Physics of the Solid State, 2000, 42[12], 2204-10)