Reduction of threading dislocation density in GaN grown on strain relaxed nanoporous GaN template

摘要

Growth of gallium nitride (GaN) on strain relaxed nanoporous GaN template by metal-organic chemical vapor deposition has produced GaN layer with 60% reduction in threading dislocation density (TDD). The porous GaN was annealed at 850℃ for 3 min in a mixed of nitrogen and ammonia ambient, which annihilated most TDs within the porous region via air-gap formation coupled with surface edge step pinning of dislocations. Enhancement of optical quality was indicated by doubled Raman intensity of E_2 phonon peak of annealed porous as compared to as-fabricated porous GaN. Besides, a redshift of 0.7 cm~(-1) in E_2 phonon peak of porous GaN with respect to as-grown GaN corresponds to a relaxation of compressive stress by 0.17±0.05 GPa. Further overgrowth of GaN on annealed porous GaN template gives high quality GaN with reduction in TDD.