The dislocation structures of GaN wafers were studied by means of transmission electron microscopy. The wafers were prepared via the hydride vapour phase epitaxy of thick GaN layers on 6H-SiC substrates, and removal of the substrate by reactive ion etching. Three main types of dislocation were observed in the GaN crystals. Threading dislocations were mainly parallel to the [00•1] direction and extended from the former interface to the crystal surface. They were of edge, screw and mixed type. Other dislocations lay on basal (00•1) planes and were located near to threading dislocations throughout the thickness of the crystal. Further dislocations lay preferentially on prismatic planes in the upper regions of the crystals.

Dislocation Structure of GaN Bulk Crystals Grown on SiC Substrates by HVPE I.Nikitina, G.Mosina, Y.Melnik, A.Nikolaev, K.Vassilevski: Materials Science and Engineering B, 1999, 61-62, 325-9