Various microscopic mechanisms for Si diffusion in GaAs and Si-induced interdiffusion in GaAs/AlAs superlattices are investigated by ab initio molecular dynamics. The dominant mechanism involves the motion of negatively charged ${\mathrm{Si}}_{\mathrm{III}\mathrm{-}}$${\mathit{V}}_{\mathrm{III}}$ pairs through second-nearest-neighbor jumps. This mechanism explains both the ability of Si to disorder superlattices regardless of whether it was introduced during growth or in-diffused afterwards and the suppression of interdiffusion by compensation doping. The computed activation energies are in very good agreement with the experimental data.

• Received 9 September 1993

DOI:https://doi.org/10.1103/PhysRevB.49.2985