[en] The influence of in situ photoexcitation on the defect structure generation in GaAs crystals implanted by Ar⁺ ions with energy of 200 keV and doses of 1x10¹³, 3x10¹³ and 5x10¹³ cm^-2 was studied by high-resolution x-ray diffraction and Rutherford backscattering spectroscopy. The in situ photoexcitation is found to provide for annihilation of Frenkel pairs that decrease a residual concentration of radiation-induced point defects. The amorphization of the damaged layer is assumed to proceed by a generation and a growth of radiation-induced point defect clusters. The vacancy- and interstitial-type clusters are spatially separated: the former are located closer to the surface than the latter ones. The in situ photoexcitation is shown to hinder the cluster growth and to stimulate diffusion of interstitials towards undamaged substrate