Energetics of self-diffusion in GaAs

Atomistic thermodynamic calculations are performed in order to examine the energetic% of self-diffusion in GaAs. An energetic assessment of the activation enthalpy of the saddle-point configuration of various modes of vacancy self-diffusion indicates second-nearest-neighbor hopping to be the energetically most favorable mechanism if vacancies are available in equilibrium concentrations. An assessment of the activation entropy indicates that normal diffusion prefactors of magnitude Do10 5-10 ’ s, cm2 s ’ are consistent with vacancy self-diffusion by second-nearest-neighbor hopping. It is proposed that self-diffusion experiments characterized by prefactors and activation energies of large magnitude, e.g., D,,=: lo’-lo8 cm* s’ and E (I z 6 eV, involve processes in which surface vacancy generation is inhibited and self-diffusion is mediated by Frenkel pair generation.