Possible mechanisms associated with the bending of threading dislocations through 90° in GaN were described. In situ ELOG using SiNx masking on a sapphire substrate and in-situ SiNx interlayer deposition on a GaN pseudo-substrate were used to reduce the threading dislocation density in GaN. The bending of threading dislocations through 90° was essential in order to reduce their numbers in the upper growing layer. The bending of threading dislocations was facilitated by a change in growth mode, i.e. predominantly 2D to 3D and then 3D to 2D. A new mechanism was tentatively proposed which could explain the bending of all types of threading dislocations (edge, screw, and mixed). This new mechanism was based on first, step formation at 3D island side facets when threading dislocations terminate there, following which, depending on the subsequent change in growth mode (3D to 2D) and the direction of the atomic ledge movement, the threading dislocations will bend over.

Mechanisms of Bending of Threading Dislocations in MOVPE-Grown GaN on (0001) Sapphire. R.Datta, C.J.Humphreys: Physica Status Solidi C, 2006, 3[6], 1750-3