Dislocation annihilation by silicon delta-doping in GaN epitaxy on Si

The addition of bursts of silicon has been observed to correlate with the reduction of threading screw dislocations during epitaxial growth of GaN on silicon by metalorganic chemical vapor deposition. The reduction is associated with bending of screw dislocations and “pairing” with equivalent neighboring dislocations with opposite Burgers vectors. This results in the formation of square dislocation loops. When the right type of dislocation is not available, the dislocation continues propagating in the original direction, leaving behind a kink at the silicon-rich position. These observations apply only to dislocations with a screw component. Edge dislocations are not affected by silicon delta-doping. A mechanism for the termination of threading screw dislocation is proposed, which involves pinning by the silicon impurities of the surface lattice steps associated with screw dislocations.