Numerous experiments on damage in semiconductors due to ion bombardment have shown quite varied material-dependent behaviour. In particular after the recovery phase, the residual damage can vary from almost crystalline to amorphous for given ion bombardment conditions [1]. We have studied both the initial cascade damage and the subsequent recovery using approximate and full molecular dynamics techniques for Si, GaAs and AlAs. These semiconductors are modelled using the Si Tersoff potential which has been modified for GaAs and AlAs. In this presentation, the results of these simulations will be given. These clearly show that AlAs sustains less damage than GaAs, in agreement with experiment.

Low energy displacement events produce simple point defects such as Frenkel pairs. Computer simulations of these events are useful as they provide information concerning the nature of damage in semiconductors, and can generate input parameters required for a theoretical study of cascades. Using molecular dynamics simulations we have investigated low energy displacement in Si, GaAs and AlAs for ejections below 32 eV. These materials are modelled using the Si Tersoff potential, which has been modified for the compound semiconductors. For each atomic species we have determined the displacement threshold energy, and its angular dependence together with an estimate of recombination distances. Several ejection processes have been identified. Their directional and energy dependencies will be discussed. The results for Si, GaAs and AlAs are compared and physical reasons are given for the similarities and differences.