Manifestation of edge dislocations in photoluminescence of GaN

A GaN layer was grown by molecular beam epitaxy on a freestanding GaN template prepared by hydride vapor-phase epitaxy. Two characteristic areas have been found in the overgrown layer: a region nearly free from dislocations and a region with the density of the edge dislocations of ∼5x109 cm-2, 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 3.35 eV. These lines are attributed to unidentified point defects trapped by the edge threading dislocations