Abstract: The radiation damage and annealing behavior of <100> Si implanted with 500 keV As₂⁺ and 250 keV As⁺ have been investigated. Experimental results show that the damage created by As₂⁺ implantation is greater than that created by As⁺ implantation. After rapid thermal annealing, the complete recovery from crystal damage, high substitution and electrical activation of implanted atoms can be obtained for both the As₂⁺ and As⁺ implantations. The carrier concentration profiles are different for the As₂⁺ and As⁺ Implanted samples, which can be explained by the rapid diffusion of impurities resulting from the serious damage enhancement induced by As₂⁺ implantation.