  Infrared (IR) radiation detectors are used in numerous applications from
thermal imaging to spectroscopic gas sensing. Obtaining high speed and
sensitivity, low-power operation and cost-effectiveness with a single
technology remains to be a challenge in the field of IR sensors. By combining
nano-thermoelectric transduction and nanomembrane photonic absorbers, we
demonstrate uncooled IR bolometer technology that is material-compatible with
large-scale CMOS fabrication and provides fast and high sensitivity response to
long-wavelength IR (LWIR) around 10 $\mu$m. The fast operation speed stems from
the low heat capacity metal layer grid absorber connecting the sub-100 nm-thick
n- and p-type Si nano-thermoelectric support beams, which convert the radiation
induced temperature rise into voltage. The nano-thermoelectric
transducer-support approach benefits from enhanced phonon surface scattering in
the beams leading to reduction in thermal conductivity, which enhances the
sensitivity. We demonstrate different size nano-thermoelectric bolometric
photodetector pixels with LWIR responsitivities, specific detectivities and
time constants in the ranges 179-2930 V/W, 0.15-3.1$\cdot10^{8}$ cmHz$^{1/2}$/W
and 66-3600 $\mu$s, respectively. We benchmark the technology against different
LWIR detector solutions and show how nano-thermoelectric detector technology
can reach the fundamental sensitivity limits posed by phonon and photon thermal
fluctuation noise.
