Surface morphology of GaN bombarded by highly charged 126Xeq+ ions

N-type GaN films bombarded with different highly charged 126Xeq+-ions（9≤q≤30） at room temperature was studied by atomic force microscopy. The experimental results show that when q exceeds the threshold value 18, remarkable swelling turns into obvious erosion in the irradiated area. On the other hand, surface disorder of GaN films strongly depends on the charge state q of ions, incident angle and ion influence, and the damage behavior of films is unrelated to the kinetic energy within the scope of experimental parameters（180 keV≤Ek≤600 keV）.For q=18, the surface morphology of the films almost does hot change at normal incidence, and at incidence angle of 30° relative to the film surface, there appears small-scale swelling in irradiated region and a low step forms between the irradiated and un-irradiated regions. For qq>18, film surface is etched, forming a deep dump with a high step with the increase of ions influence. Unambiguous indentations relevant to the ion influence on the step appear. Furthermore, the step height is proportional to the ion influence approximately and is much higher for tilted incidence than normal incidence.