Two type of top layers, namely, undoped and Si‐doped GaAs layers, were grown, respectively, on a Be‐doped epilayer by molecular beam epitaxy, and the effects of impurities of Be and Si on the creation of Ga interstitials IGa and Ga vacancies VGa during the annealing of the specimens were investigated by a slow positron beam. The concentration of VGa created from the surface of the undoped GaAs during the annealing decreases drastically when the annealed GaAs was kept at room temperature for one month. This implies that the Be atoms diffusing to the undoped GaAs during the growth and/or the annealing cause the creation of IGa in the undoped layer and it makes the recombination with VGa. On the other hand, no decrease in the concentration of VGa was observed in the Si‐doped GaAs. These support the creation of IGa and of VGa, respectively, in the Be‐diffused GaAs and in Si‐diffused GaAs.