Damage accumulation in wurtzite films which were bombarded with 0.5MeV Bi and 1MeV Bi2 ions (to test the so-called molecular effect) was studied by means of Rutherford back-scattering channelling spectrometry. The results showed that an increase in the density of collision cascades dramatically enhanced the level of implantation-produced lattice disorder. This was attributed to an increase in the defect clustering efficiency with increasing density of ion-beam generated point defects and/or to collective non-linear energy spike processes. It was concluded that a marked effect of the density of collision cascades had to be taken into account in order to estimate correctly the implantation-produced lattice disorder in GaN.

Effect of the Density of Collision Cascades on Implantation Damage in GaN. S.O.Kucheyev, J.S.Williams, A.I.Titov, G.Li, C.Jagadish: Applied Physics Letters, 2001, 78[18], 2694-6