  Plasmonic sensing in the infrared region employs the direct interaction of
the vibrational fingerprints of molecules with the plasmonic resonances,
creating surface-enhanced sensing platforms that are superior than the
traditional spectroscopy. However, the standard noble metals used for plasmonic
resonances suffer from high radiative losses as well as fabrication challenges,
such as tuning the spectral resonance positions into mid- to far-infrared
regions, and the compatibility issue with the existing complementary
metal-oxide-semiconductor (CMOS) manufacturing platform. Here, we demonstrate
the occurrence of mid-infrared localized surface plasmon resonances (LSPR) in
thin Si films hyperdoped with the known deep-level impurity tellurium. We show
that the mid-infrared LSPR can be further enhanced and spectrally extended to
the far-infrared range by fabricating two-dimensional arrays of
micrometer-sized antennas in a Te-hyperdoped Si chip. Since Te-hyperdoped Si
can also work as an infrared photodetector, we believe that our results will
unlock the route toward the direct integration of plasmonic sensors with the
one-chip CMOS platform, greatly advancing the possibility of mass manufacturing
of high-performance plasmonic sensing systems.
