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

Abstract

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°C for 3min 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 E2 phonon peak of annealed porous as compared to as-fabricated porous GaN. Besides, a redshift of 0.7cm−1 in E2 phonon peak of porous GaN with respect to as-grown GaN corresponds to a relaxation of compressive stress by 0.17±0.05GPa. Further overgrowth of GaN on annealed porous GaN template gives high quality GaN with reduction in TDD.