A GaN layer was grown by molecular beam epitaxy on a free-standing GaN template prepared by hydride vapor-phase epitaxy. Two characteristic areas were found in the overgrown layer: a region nearly free from dislocations and a region with the density of the edge dislocations of some 5 x 109/cm2, as determined by transmission electron microscopy. Low-temperature photoluminescence spectrum from the former contained only well-known exciton lines, whereas the spectrum of the defective area contained additional lines at 3.21 and 3.35eV. These lines were attributed to unidentified point defects trapped by the edge threading dislocations.

Manifestation of Edge Dislocations in Photoluminescence of GaN. M.A.Reshchikov, D.Huang, L.He, H.Morkoç, J.Jasinski, Z.Liliental-Weber, S.S.Park, K.Y.Lee: Physica B, 2005, 367[1-4], 35-9