Threading dislocation evolution during patterned GaN nanocolumn growth and coalescence overgrowth with metal-organic chemical vapour deposition was studied by comparing nanocolumn and coalescence overgrowth samples having various nanocolumn diameters and spacings. From measurements of depth-dependent X-ray diffraction and cross-sectional transmission electron microscopy, it was deduced that the threading dislocation density in an nanocolumn depended upon the patterned hole size for nanocolumn growth. Also, threading dislocation formation at the beginning of coalescence overgrowth was related to the nanocolumn spacing. Although the threading dislocation density at the bottom of the overgrown layer was weakly dependent upon nanocolumn size and spacing at its top surface, the threading dislocation density strongly depended upon nanocolumn size. For overgrowth samples of various nanocolumn diameters and spacings, at a given nanocolumn diameter/spacing ratio, that having the smallest size and spacing led to the lowest threading dislocation density and the largest lateral domain size.

Threading Dislocation Evolution in Patterned GaN Nanocolumn Growth and Coalescence Overgrowth. Y.S.Chen, W.Y.Shiao, T.Y.Tang, W.M.Chang, C.H.Liao, C.H.Lin, K.C.Shen, C.C.Yang, M.C.Hsu, J.H.Yeh, T.C.Hsu: Journal of Applied Physics, 2009, 106[2], 023521