Effect of the density of collision cascades on implantation damage in GaN

Damage accumulation in wurtzite GaN films bombarded with 0.5 MeV Bi-1 and 1 MeV Bi-2 ions (the so-called molecular effect) is studied by Rutherford ba ckscattering/channeling spectrometry. Results show that an increase in the density of collision cascades dramatically enhances the level of implantati on-produced lattice disorder in GaN. This effect is attributed to (i) an in crease in the defect clustering efficiency with increasing density of ion-b eam-generated point defects and/or (ii) to collective nonlinear energy spik e processes. Such a strong influence of the density of collision cascades i s important to take into account for a correct estimation of implantation-p roduced lattice disorder in GaN. (C) 2001 American Institute of Physics.