Defect clustering in GaN irradiated with O+ ions

Transmission electron microscopy (TEM) was used to study microstructures formed in GaN irradiated with 600-keV O+ ions at room temperature. Three types of defect clusters were identified in the irradiated GaN: (i) basal-plane stacking faults with dimensions ranging from 5 to 30 nm, (ii) pyramidal dislocation loops, and (iii) local regions of highly disordered material. High-resolution TEM imaging clearly revealed that one type of the basal-plane stacking faults corresponded to insertion of one extra Ga-N basal plane in the otherwise perfect GaN lattice. The interpretation of these results indicated that interstitials of both Ga and N preferentially condensed on the basal plane to form a new layer of Ga-N under these irradiation conditions. The formation of these extended defects and their interactions with the point defects produced during irradiation contributed to a dramatic increase in the dynamic recovery of point defects in GaN at room temperature.