Possible mechanisms which were 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 onto 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 2-dimensional to 3-dimensional and then 3-dimensional to 2-dimensional. A new mechanism was tentatively proposed which could explain the bending of all types of threading dislocation (edge, screw or mixed). This new mechanism was based upon step-formation at 3-dimensional island side facets when threading dislocations terminated there, following which (depending upon the subsequent change in growth mode, such as 3-dimensional to 2-dimensional, and the direction of atomic ledge movement) the threading dislocations bent over.

Mechanisms of Bending of Threading Dislocations in MOVPE-Grown GaN on (00▪1) Sapphire. R.Datta, C.J.Humphreys: Physica Status Solidi C, 2006, 3[6], 1750-3