[en] Defects created in ion implanted and laser irradiated GaAs layers have been investigated by means of optical methods and the Rutherford backscattering channeling technique. The paper was presented at the International Conference on radiation effects in insulators, Guildford (United Kingdom) 1985. The optical measurements show characteristic near-edge optical properties which are explained assuming the existence of high concentrations of anti-site defects and vacancies and/or complexes of these defects, which are produced during the irradiation processes. The backscattering data also indicate large concentrations of point defects with small distances from the lattice site. (U.K.)