A method of semiconductor junction formation in RTA process for fabrication of solar cells provides for delivery of inert gases in the vicinity of the Si wafer while dopant species are being driven form a dopant source into the surface of the wafer irradiated by a laser beam. The laser beam is emitted by CW- or pulsed operated lasers including fiber lasers operative to provide annealing and diffusion operation. Optionally, the passivation of the surface and formation of the antireflection coating are performed simultaneously with the penetration the dopant species.