The annealing behavior of arsenic‐implanted silicon using a CO laser is investigated and compared to CO2laser annealing. The irradiation time dependence of the surface carrier concentration and electron mobility on the laser wavelength and substrate doping density is shown to be a direct consequence of free carrier absorption. The two infrared laser annealing methods are found to result in identical electrical characteristics, which are comparable to that obtained by 30‐min furnace anneals at 800 °C.