Extended infrared responses in Er/O-hyperdoped Si at room temperature

Silicon photonics has become the preferred candidate for technologies applicable to multifarious fields. However, the applications are strictly limited by the intrinsic in-band photo effect of silicon. Herein, near-infrared photodetectors that break through the silicon bandgap by Er/O hyperdoping are fabricated, potentially extending their applications into telecommunications, low-light-level night vision, medical treatment, and others. Er/O-hyperdoped silicon was achieved as an infrared light absorption layer through ion implantation. The lattice damage caused by ion implantation was repaired by a deep cooling process in which high-temperature samples were cooled by helium flushing cooled by liquid nitrogen. Traditional junction and metallization processes were performed to form a photodiode. We demonstrate that the device has a spectral range up to the wavelength of 1568 nm, a maximum responsivity of 165 µA/W at 1310 nm, and 3 dB cutoff bandwidth up to 3 kHz. Finally, temperature-dependent optical-electrical characteristics were measured to demonstrate the activation mechanism of Er/O in silicon. This Letter proves silicon's potential in realizing extended infrared detection at room temperature, and it provides a possible way to fabricate infrared optoelectronics and signal processing integrated chips on a CMOS (complementary metal-oxide-semiconductor) platform.