A defected zone in hydride vapor phase epitaxy deposited GaN located near an interface with a SiC substrate was investigated by transmission electron microscopy for both plan-view and cross-section specimens. The predominant defects in the defected zone were dislocations and stacking fault-type interfaces. Analysis of the defects by a moiré contrast and high-resolution imaging had suggested that the interfaces resulted from the process of coalescence and overgrowth of three-dimensional nucleated islands. The islands differ by a translation with respect to the reference (substrate) lattice, and therefore their coalescence resulted in the formation of domains separated by stacking fault-type boundaries. For the hydride vapor phase epitaxy process used in depositing the specimens studied, it was deduced that the islands adopted the shape of {11▪l}-faceted truncated pyramids. Continued coalescence and overgrowth of the nonequivalent by translation domains result in a substructure of connected (00▪1) and {11▪0} stacking faults and threading dislocations. The density of these defects decreases with continued coalescence as the growth of GaN progresses, and thus determines the effective thickness of the defected zone. It was expected that the extent of such defected zones would depend upon the nucleation frequency and anisotropic growth rate of different crystallographic facets.

Transmission Electron Microscopy Study of a Defected Zone in GaN on a SiC Substrate Grown by Hydride Vapor Phase Epitaxy. L.A.Bendersky, D.V.Tsvetkov, Y.V.Melnik: Journal of Applied Physics, 2003, 94[3], 1676-85