A method and system for doping semiconductor materials using microwave exposure. In some embodiments, the surface of a semiconductor substrate coated with a layer of dopant material is exposed to a beam of microwave radiation, with the frequency of the microwave radiation chosen to coincide with a microwave absorption resonance of the dopant. A gyrotron is a preferred source of monochromatic microwaves capable of delivering the appropriate the power density. Under this microwave exposure, the dopant heats up and diffuses into the semiconductor. Since only the dopant is selectively excited, the atoms of the crystal lattice remain cooler. Additional cooling can be provided by a flow of cooling gas onto the surface. When the electric field of the microwave exposure is high enough to overcome the potential barrier of interstitial diffusion within the crystal, the dopants migrate to vacancies in the crystal lattice, and the semiconductor material becomes activated.