Improving crystallinity of femtosecond-laser hyperdoped silicon via co-doping with nitrogen

Laser hyperdoped silicon with high crystallinity in doped layer is obtained by method of femtosecond laser irradiation in NF3/SF6 gas mixture. SIMS measurement indicates nitrogen and sulfur dopants are incorporated into the top layer of about 300 nm at concentrations above 1019 cm−3, SAD and Raman Spectrum results show that there is approximately crystalline silicon in the doped layer. The crystallinity in doped layer of the laser co-hyperdoped silicon is almost same as that of the annealed sample at 800 K prepared in SF6. The improvement of crystallinity is attributed to the hyperdoped nitrogen, which is effectively on repairing the defects in the doped layer. The light absorption is more than 95% over the range of 300-1100 nm, and about 80% in the 1200-2500 nm wavelength range.