Extended defect systems, which included threading dislocations and mosaic structures in GaN epilayers grown onto (00▪1) sapphire substrates by MOCVD, were investigated by means of transmission electron microscopy and atomic force microscopy. The strain relaxation of extended defect systems with various degrees of order of mosaic structure was found to differ noticeably. For extended defect systems with poor degrees (greater than 0.34) of order of the mosaic structure, 3D-growth with the formation of large agglomerates of the mosaic structure domains in the regions near to the threading (screw) dislocations occurred. Numerous domain dislocation boundaries in these structures were observed. Coherent concordance of domains, with the formation of dilatation boundaries was more typical of extended defect systems with better degrees (less than 0.34) of order of the mosaic structure. Moreover, 2D-growth with the formation of additional growth steps and the involvement of screw dislocations was observed. The optical and electrical properties of GaN epilayers correlate well with these structural peculiarities.

Peculiarities of Extended Defect System in III-Nitrides with Different Degrees of Order of Mosaic Structure. A.V.Ankudinov, A.I.Besyulkin, A.G.Kolmakov, W.V.Lundin, V.V.Ratnikov, N.M.Shmidt, A.A.Sitnikova, A.N.Titkov, A.S.Usikov, E.B.Yakimov, E.E.Zavarin, R.V.Zolotareva: Physica B, 2003, 340-342, 462-5