On the amorphization process in Al0.6Ga0.4As/GaAs heterostructures

The amorphization mechanism operative in Al0.6Ga0.4As/GaAs structures has been studied by using ion implantation at 77 K with different ion masses (Kr and Ar) and energies (1 endash 3 MeV). The damage produced by these implantations was examined by using a combination of ion channeling and cross-sectional transmission electron microscopy. For all implantation conditions, the damage accumulation produced by implantation at 77 K increases with depth into the Al0.6Ga0.4As layer. Neither point defects nor energetically dense cascade events by themselves were found to be sufficient to drive Al0.6Ga0.4As amorphous at 77 K. Amorphization occurred only when a high density of energetically dense cascade events were superimposed on a high total defect population. These conditions were satisfied deep in the layer and only for the 1.5 MeV Kr ion implantation. With the exception of the amorphous material, the damage structure produced at 77 K recovered on warming to room temperature. The recovered structure consisted of dislocation loops or planar defects. copyright 1998 American Institute of Physics