Enhanced responsivity of co-hyperdoped silicon photodetectors fabricated by femtosecond laser irradiation in a mixed SF6/NF3 atmosphere

Abstract

Co-hyperdoped silicon is fabricated on single crystalline Si substrate by using femtosecond-laser pulses in a mixed gas of S F 6 and N F 3 with different ratios. With the increase of the proportion of N F 3 in the mixed gas, the co-hyperdoped silicon shows increased crystallinity but decreased sub-bandgap absorption. Photodetectors are fabricated based on these samples without high-temperature thermal annealing. With the increase of the proportion of N F 3 , the photoelectric response first increases and then decreases. Photodetectors based on the co-hyperdoped ( N F 3 / S F 6 , 35/35 kPa) material without high-temperature thermal annealing demonstrate high performance on photoresponsivity ( 6 A W − 1 @ − 5 V for 1050 nm), which is an order of magnitude higher compared with the photodetector made from S-hyperdoped silicon. The photoconductive gain accounts for the high responsivity.