We study structural disorder in ZnO bombarded at room temperature with $1.3\text{keV}∕\text{amu}$ atomic $\text{P}$ and cluster ${\text{PF}}_n$ ($n=2$ and 4) ions. Rutherford backscattering/channeling spectrometry results show that the density of collision cascades has a negligible effect on the damage buildup in the crystal bulk in the dose range resulting in $\sim 1.5-15$ displacements per atom. Hence, the amount of stable post-implantation disorder in the bulk can be predicted based on ballistic calculations. In contrast, the cascade density affects radiation damage in the near-surface region. An intermediate defect peak between the expected surface and bulk peaks of disorder forms for ion irradiation conditions with dense cascades.

A systematic investigation of radiation hardness of Schottky barrier diodes and GaN epitaxial layers is carried out by employing in-situ electrical resistivity and cross sectional transmission electron microscopy (XTEM) microstructure measurements. The change in the current transport mechanism of Au/n-GaN Schottky barrier diodes due to irradiation is reported. The role of irradiation temperature and ion type was also investigated. Creation of damage is studied in low and medium electron energy loss regimes by selecting different ions, Ag (200 MeV) and O (100 MeV) at various fluences at two irradiation temperatures (80 K and 300 K). GaN resistivity increases up to 6 orders of magnitude under heavy Ag ions. Light O ion irradiation has a much lower influence on sheet resistance. The presence of isolated defect clusters in irradiated GaN epilayers is evident in XTEM investigation which is explained on the basis of the thermal spike model.

We have studied defect production during single atomic and molecular ion irradiation having an energy of 50 eV/amu in GaN by molecular dynamics simulations. Enhanced defect recombination is found in GaN, in accordance with experimental data. Instantaneous damage shows non-linearity with different molecular projectile and increasing molecular mass. Number of instantaneous defects produced by the ${\text{PF}}_4$ molecule close to target surface is four times higher than that for ${\text{PF}}_2$ molecule and three times higher than that calculated as a sum of the damage produced by one P and four F ion irradiation ($\mathrm{P}+4\times \mathrm{F}$ ). We explain this non-linearity by energy spike due to molecular effects. On the contrary, final damage created by ${\text{PF}}_4$ and ${\text{PF}}_2$ shows a linear pattern when the sample cools down. Total numbers of defects produced by Ag and ${\text{PF}}_4$ having similar atomic masses are comparable. However, defect-depth distributions produced by these species are quite different, also indicating molecular effect.