Nano-thermoelectric infrared bolometers

TL;DR

This paper introduces a nano-thermoelectric infrared bolometer technology that combines nanomembrane photonic absorbers with thermoelectric transduction, achieving high sensitivity, fast response, and CMOS compatibility for LWIR detection.

Contribution

The work presents a novel uncooled IR bolometer design using nano-thermoelectric transducers and nanomembrane absorbers, enhancing sensitivity and speed while being compatible with large-scale CMOS fabrication.

Findings

Achieved LWIR responsivities of 179-2930 V/W.

Demonstrated time constants of 66-3600 microseconds.

Reached sensitivity limits set by phonon and photon thermal noise.

Abstract

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.