Coalescence-induced planar defects in GaN layers grown on ordered arrays of nanorods by metal–organic vapour phase epitaxy

The planar defect structure of coalesced GaN layers fabricated on ordered arrays of nanorods and grown by metal-organic vapour phase epitaxy has been studied using conventional and high-resolution transmission electron microscopy. During the process of coalescence, a boundary was created between two pyramids, where I1-type basal plane stacking faults propagating through the overgrown layers are terminated by Frank-Shockley partial dislocations. According to multislice HRTEM simulations of experimental observed images in the [ ] zone axis, the step-and hairpin-shaped basal prismatic stacking faults with inclined { } plane are consistent with Drums structural model, which has a lower formation energy compared with the model proposed by Amelinckx. Based on the observation that there are no stacking faults in the overgrown layers prior to the nanopyramid merging, the mechanism of coalescence induced stacking faults is proposed. This research contributes to the understanding of planar defect formation in III-nitride semiconductor grown by a coalescence process.