Pulsed electron beam with an energy fluence of 1.0 J/cm2was irradiated on (100) and (111) Si implanted with 1×1016As+/cm2at 40 keV. Highly dopedn+layers with peak carrier concentrations of 8×1020/cm3and 7×1020/cm3for (100) and (111) samples were obtained, respectively, after electron beam irradiation. The effect of additional thermal treatment on electrical behaviors and crystalline quality of electron‐beam annealed samples has been investigated. Carrier concentration decreased with increasing additional annealing temperature up to 800 °C and it increased above 800 °C, where the system approached a thermal equilibrium and at the same time thermal diffusion of As occurs. Rutherford backscattering spectrometry (RBS) and transmission electron microscopy (TEM) observations revealed that no residual damage remained after electron beam irradiation but dislocation loops were formed during the course of additional thermal annealing.