Annihilation mechanism of threading dislocations in AlN grown by growth form modification method using V/III ratio

High-quality AlN layers with atomically flat surface were grown on a c-plane sapphire substrate by high-temperature metal-organic vapor phase epitaxy (HT-MOVPE). Controlling V/III ratio during growth led to change the growth rate for each facet resulting in the change of the macroscopic form of grain at the transition V/III ratio. The threading dislocations were annihilated with the formation of dislocation loops at the changing of grain form. AlN crystallinity was improved due to the reason that small AlN grains were incorporated by the big AlN grains during growth. These phenomena were confirmed by transmission electron microscopy (TEM) and atomic force microscopy (AFM).