The formation of radiation damage in GaN during successive bombardment by light ions of various energies

We present the results of investigation of radiation damage accumulation in GaN during its sequential co-implantation with fluorine ions of two different energies. This process is proved to be a non-commutative one, i.e. a clear difference in the amount of resulting damage is found, that depends on the sequence of the energy of bombarding ions used. Possible mechanism of the effect revealed is proposed and discussed. This mechanism also explains well experimentally established saturation of the bulk defect peak height in gallium nitride at a level remarkably below the full amorphization.