Highly responsive tellurium-hyperdoped black silicon photodiode with single-crystalline and uniform surface...

Femtosecond laser hyperdoped silicon, also known as the black silicon (BS), has a large number of defects and damages, which results in unstable and undesirable optical and electronic properties in photonics platform and optoelectronic integrated circuits (OEICs). We propose a novel method that elevates the substrate temperature during the femtosecond laser irradiation and fabricates tellurium (Te) hyperdoped BS photodiodes with high responsivity and low dark current. At 700 K, uniform microstructures with single crystalline were formed in the hyperdoped layer. The velocity of cooling and resolidification is considered as an important role in the formation of a high-quality crystal after irradiation by the femtosecond laser. Because of the high crystallinity and the Te hyperdoping, a photodiode made from BS processed at 700 K has a maximum responsivity of 120.6 A/W at 1120 nm, which is far beyond the previously reported Te-doped silicon photodetectors. In particular, the responsivity of the BS photodiode at 1300 nm and 1550 nm is 43.9 mA/W and 56.8 mA/W with low noise, respectively, which is valuable for optical communication and interconnection. Our result proves that hyperdoping at a high substrate temperature has great potential for femtosecond-laser-induced semiconductor modification, especially for the fabrication of photodetectors in the silicon-based photonic integration circuits.