  Si-based photodetectors satisfy the criteria of low-cost and
environmental-friendly, and can enable the development of on-chip complementary
metal-oxide-semiconductor (CMOS)-compatible photonic systems. However,
extending their room-temperature photoresponse into the mid-wavelength infrared
(MWIR) regime remains challenging due to the intrinsic bandgap of Si. Here, we
report on a comprehensive study of a room-temperature MWIR photodetector based
on Si hyperdoped with Te. The demonstrated MWIR p-n photodiode exhibits a
spectral photoresponse up to 5 {\mu}m and a slightly lower detector performance
than the commercial devices in the wavelength range of 1.0-1.9 {\mu}m. We also
investigate the correlation between the background noise and the sensitivity of
the Te-hyperdoped Si photodiode, where the maximum room-temperature specific
detectivity is found to be 3.2 x 10^12 cmHz^{1/2}W^{-1} and 9.2 x 10^8
cmHz^{1/2}W^{-1} at 1 {\mu}m and 1.55 {\mu}m, respectively. This work
contributes to pave the way towards establishing a Si-based broadband infrared
photonic system operating at room temperature.
