Nature of planar defects in ion-implanted GaN

Wurtzite GaN films bombarded with keV ions were studied by high-resolution transmission electron microscopy. Results showed that irradiation under a wide range of implant conditions (such as ion mass, dose, and implant temperature) led to the formation of planar defects which were parallel to the basal plane of the wurtzite structure. For all implant conditions studied, all planar defects observed in the ∼20 nm thick near-surface layers of GaN were interstitial in nature and had Burgers vectors of either 1/2[0001] or 1/6(2203). Although the nature of these irradiation-produced planar defects appeared to be independent of implant conditions, irradiation parameters were found to influence the average defect size and density. In particular, larger planar defects were observed for higher irradiation temperatures. Possible physical mechanisms for the formation of such planar defects are discussed.