Transmission Electron Microscopy Study of Nonpolar a-Plane GaNGrown by Pendeo-Epitaxy on (112_0) 4H-SiC

Pendeo-epitaxy has been applied to nonpolar a-plane GaN layers in order to observe if such process will lead to defect reduction in comparison with direct growth on this plane. Uncoalesced and coalesced a-plane GaN layers with thicknesses 2{micro}m and 12{micro}m, respectively have been studied by conventional and high resolution electron microscopy. The following structural defects have been observed in pendeo-epitaxial layers: (1) basal stacking faults, (2) threading dislocations and (3) prismatic stacking faults. Drastic decrease of threading dislocation density and stacking faults have been observed in 'wing' areas with respect to 'seed' areas. Cross-section images reveal cracks and voids at the areas where two coalesced wings meet each other. High resolution electron microscopy shows that the majority of stacking faults are low-energy planar defects of the types I{sub 1}, I{sub 2} and I{sub 3}. The I{sub 3} type basal stacking fault, predicted theoretically, has been observed experimentally for the first time.