A new multi-step MOCVD method for growing GaN was used to suppress threading dislocations in GaN epilayers on c -plane sapphire. A nucleation island density of as low as 2.5 x 107/cm2 was reported. Developed subsequent overgrowth prevents the formation of new islands and stimulates the inclination of threading dislocations inside nucleation islands before their coalescence. GaN epilayers with a threading dislocation density of 5.0 x 107/cm2 were grown by the method. Nucleation island morphology and threading dislocation density were analyzed by atomic force microscopy. Transmission electron microscopy was used to support the results for the threading dislocation density and to evaluate the epitaxial relationship of the GaN films.

Multistep Method for Threading Dislocation Density Reduction in MOCVD Grown GaN Epilayers. T.Lang, M.A.Odnoblyudov, V.E.Bougrov, A.E.Romanov, S.Suihkonen, M.Sopanen, H.Lipsanen: Physica Status Solidi A, 2006, 203[10], R76-8