Investigation of the sulfur doping profile in femtosecond-laser processed silicon

In this letter, we demonstrate that silicon can be doped with electrically active sulfur donors beyond the solubility limit of 3 × 1016 cm−3. We investigate the sulfur doping profile at the surface of femtosecond-laser processed silicon with secondary ion mass spectroscopy (SIMS) and capacitance-voltage measurements. SIMS confirms previous observations that the fs-laser process can lead to a sulfur hyperdoping of 5×1019 cm−3 at the surface. Nevertheless, the electrical measurements show that less than 1% of the sulfur is electrically active as a donor.