Dirac plasmon-assisted dynamically tunable LWIR photodetection at room temperature based on nanopatterned monolayer graphene*

The detection of long-wave infrared (LWIR) photons is challenging at room temperature due to the low photon energy. The uncooled microbolometers suffer from low sensitivity, slow response, and tedious multi-step complex lithographic processes. Mercury Cadmium Telluride (MCT) detector needs cryogenic cooling and complex, low-yield ROIC hybridization. The newly emerging colloidal quantum dot (CQD) based detectors suffer from high dark currents, inefficient carrier transport, and poor LWIR performance. We present a spectrally selective ultrafast LWIR detector based on CVD grown large area nanopatterned graphene (NPG). By introducing nanopatterns (circular holes arranged in a hexagonal array), the absorption in the LWIR band for monolayer NPG coupled to the Fabry Perot cavity is enhanced up to 80% because of excitation of cavity –coupled localized surface plasmons (LSPs) around the edges of circular holes. This asymmetric device’s active detector area consists of partially nanopatterned graphene.  The LSPs on the nanopatterned side create hot carriers that give rise to the Seebeck effect at room temperature, achieving a large responsivity of R ≈ 10⁴ V/W, a detectivity exceeding D* ≈ 10⁹ Jones, and an ultrafast response time of the order of 100 ns in 8-12 μm band.