Energetics of self-diffusion in GaAs

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Abstract
Atomistic thermodynamic calculations are performed in order to examine the energetics 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 D0≂10−5–10−1 s, cm2 s−1 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., D0≂107–108 cm2 s−1 and Ea ≊ 6 eV, involve processes in which surface vacancy generation is inhibited and self‐diffusion is mediated by Frenkel pair generation.