MD simulation of ion implantation damage in AlGaAs: III. Defect accumulation and amorphization

The defect accumulation and amorphization in (0 0 1)AlxGa1−xAs due to irradiation with 200 keV Ar ions at 20 K is investigated with the help of classical molecular dynamics computer simulation using a modified Tersoff potential. The amount of disorder as a function of the number of displacements per atom has been calculated for x = 0, 0.2, 0.5, 0.75, 0.9 and 1.0. The results reasonably agree with the corresponding RBS data from the literature for x ⩽ 0.9, however, they completely disagree in the case of x = 1. An artificial increase of thermally activated processes shows that thermal annealing during the irradiation may be responsible for the outstanding behavior of AlAs. In addition, the structure of the damage is investigated by visualizing the amorphous clusters and their evolution. It is shown that dynamic annealing does exist. It is negligible for x = 0 but it becomes more and more important with increasing Al content x. Furthermore, it is shown that the generation of damage is supported by pre-damage. This effect dominates the dynamic annealing for x ⩽ 0.5.