  The requirements for broadband photodetection are becoming exceedingly
demanding in hyperspectral imaging. Whilst intrinsic photoconductor arrays
based on mercury cadmium telluride represent the most sensitive and suitable
technology, their optical spectrum imposes a narrow spectral range with a sharp
absorption edge that cuts their operation to < 25 um. Here, we demonstrate a
giant ultra-broadband photoconductivity in twisted double bilayer graphene
heterostructures spanning a spectral range of 2 - 100 um with internal quantum
efficiencies ~ 40 % at speeds of 100 kHz. The giant response originates from
unique properties of twist-decoupled heterostructures including pristine,
crystal field induced terahertz band gaps, parallel photoactive channels, and
strong photoconductivity enhancements caused by interlayer screening of
electronic interactions by respective layers acting as sub-atomic spaced
proximity screening gates. Our work demonstrates a rare instance of an
intrinsic infrared-terahertz photoconductor that is complementary
metal-oxide-semiconductor compatible and array integratable, and introduces
twist-decoupled graphene heterostructures as a viable route for engineering
gapped graphene photodetectors with 3D scalability.
