A 220µm-thick gallium nitride layer was homo-epitaxially re-grown on the Ga-polar face of a 200µm-thick free-standing c-plane GaN by hydride vapour-phase epitaxy. The boundary of the biaxial stress distribution in the GaN substrate after re-growth was clearly distinguished. One half part, the re-grown GaN, was found to be more compressive than the other half part, the free-standing GaN. Additionally, the densities of the screw and mixed dislocations reduced from 2.4 x 107 to 6 x 106/cm2 after re-growth. Furthermore, the yellow band emission almost disappeared, accompanied by a peak emission at approximately 380nm related to the edge dislocation was under slightly improved in re-grown GaN. It was concluded that the reduction of the dislocation defects and Ga vacancies and/or O impurities were the two main reasons for the higher compressive stress in the re-grown GaN than in the free-standing GaN; causing the curvature of the GaN substrate to be twice as concave after re-growth.

Stress and Defect Distribution of Thick GaN Film Homoepitaxially Regrown on Free-Standing GaN by Hydride Vapor Phase Epitaxy. K.M.Chen, Y.H.Yeh, Y.H.Wu, C.H.Chiang, D.R.Yang, Z.S.Gao, C.L.Chao, T.W.Chi, Y.H.Fang, J.D.Tsay, W.I.Lee: Japanese Journal of Applied Physics, 2010, 49[9] 091001