A new approach for semiconductor processing is described in which a melt is created at a semiconductor-metal (S-M) interface by shining light of a suitable spectrum from the semiconductor side. The melt can be controlled and confined to a thin region in the vicinity of the interface by controlling the energy delivered to the interface. The interface region regrows epitaxially on silicon as a Si-metal alloy. This phenomenon appears to be an optically induced effect. The interface reaction is greatly diminished if the light is incident from the metal side. This effect is applied to form low resistivity contacts to N+/ P type solar cells in a one-step process.