Strong evidence for amphoteric native defect reactions is obtained by photoluminescence analysis of Si-doped GaAs samples (n≈1.5×1018 cm-3) annealed under different conditions. Annealing in excess As4 vapor creates a large concentration of Ga vacancies, making possible the transformation of this defect into an As vacancy and an As antisite defect. Similarly, As vacancies generated at high concentration during annealing under Ga-rich conditions are transformed into Ga vacancies and Ga antisite defects. Photoluminescence intensities associated with the corresponding defects are in qualitative agreement with the predictions of the mass action law applied to the amphoteric native defect reactions. © 1998 American Institute of Physics.