The diffusion of implanted zinc in GaAs is studied and modeled for annealing temperatures of 625 through 850 °C. Secondary ion mass spectrometry data for the annealed profiles are presented. The substitutional interstitial diffusion (SID) mechanism is used to explain how the deviation of the local gallium interstitial concentration from its equilibrium value regulates the Zn diffusion. We are able to simulate both the box shaped profiles resulting from high temperature anneals and the kink-and-tail profiles resulting from lower temperature anneals. The simulation results have allowed us to determine Arrhenius relations for: the intrinsic diffusion coefficient for implanted Zn,DZnint=0.6075 exp(−3.21 eV/kBT) cm2 s−1; the equilibrium Ga interstitial concentration,CIGa*=7.98×1030 exp(−3.47 eV/kBT)cm−3; and the Ga interstitial diffusion coefficient,DIGa=0.4384 exp(−2.14 eV/kBT)cm2 s−1. ©1997 American Institute of Physics.