Controlling dopant profiles in hyperdoped silicon by modifying dopant evaporation rates during pulsed laser melting

We describe a method to control the sub-surface dopant profile in “hyperdoped” silicon fabricated by ion implantation and pulsed laser melting. Dipping silicon ion implanted with sulfur into hydrofluoric acid prior to nanosecond pulsed laser melting leads to a tenfold increase in the rate of sulfur evaporation from the surface of the melt. This results in an 80% reduction of the near-surface dopant concentration, effectively embedding the hyperdoped region in a layer up to 180 nm beneath the surface. This method should facilitate the development of blocked impurity band devices.