Epitaxial layers of Si-doped material on an (00•1) sapphire substrate were studied by using an HCl-vapour etching technique, scanning electron microscopy, atomic force microscopy and transmission electron microscopy. Three kinds of distinctive etch pit were found, which corresponded to 3 different types of threading dislocation: edge, mixed and screw. The photoluminescence intensity increased with a decrease in the numbers of etch pits which corresponded to mixed and screw dislocations. However, the number of etch pits which corresponded to edge dislocations did not change. It was concluded that threading dislocations with screw-component Burgers vectors acted as strong non-radiative centres in epitaxial layers whereas edge dislocations, which were in the majority, did not act as non-radiative centres.

Characterization of Threading Dislocations in GaN Epitaxial Layers T.Hino, S.Tomiya, T.Miyajima, K.Yanashima, S.Hashimoto, M.Ikeda: Applied Physics Letters, 2000, 76[23], 3421-3