The radiation damage formation upon low temperature ion implantation and neutron irradiation has been compared for
GaN and ZnO. Both materials exhibit strong dynamic annealing effects during implantation, even at 15 K, leading to
high amorphisation thresholds. The damage build-up with fluence was found to proceed in a similar way for GaN and
ZnO, both showing two saturation regimes below the amorphisation level where, over wide fluence regions, the damage
level increases only very slowly. For low fluences the damage accumulation rate is similar for both materials. For higher
fluences, on the other hand, GaN shows considerably higher damage levels and finally collapses into an amorphous
structure while ZnO remains single crystalline up to the highest fluence of 7×1016 Ar/cm2.
Neutron irradiation produces similar defects as ion implantation but within the entire sample while the defect density is
much lower. The main effect of irradiation on the structural properties of GaN is an expansion of the c-lattice parameter.
Optical properties are significantly deteriorated after irradiation and only recover partially after annealing. ZnO does not
suffer such a pronounced change of the lattice parameters but reveals a strong deterioration of the surface, possibly due
to blistering and exfoliation. At the same time the optical properties are less affected than for GaN. The near band edge
emission is partly quenched but recovers to a large extend after annealing while broad defect bands are observed below
the bandgap for irradiated samples, before and after annealing.