We model the indiffusion of arsenic vacancies and their interaction with the midgap electron trap EL2 in GaAs samples that occurs during unprotected and proximity high‐temperature anneals. From fits to existing data we find the diffusive capture ofVAsby EL2 to be inhibited by a large (≳1 eV) repulsive barrier of unknown origin. In conjunction with other results from the literature we estimate the diffusivity ofVAsto be 4×10−3exp(−1.8 eV/kT) cm2/s, a value uncertain by at least an order of magnitude. ©1996 American Institute of Physics.