Plasmonically enhanced tunable spectrally selective NIR and SWIR photodetector based on intercalation doped nanopatterned multilayer graphene

We present a proof of concept for a spectrally selective near-infrared (NIR) and short-wavelength infrared (SWIR) photodetector based on nanopatterned multilayer graphene intercalated with FeCl$_3$ (NPMLG-FeCl$_3$), enabling large modulation p-doping of graphene. The localized surface plasmons (LSPs) on the graphene sheets in NPMLG-FeCl$_3$ allow for electrostatic tuning of the photodetection in the NIR and SWIR regimes from $\lambda =1.3$ $\mu$m to 3 $\mu$m, which is out of range for nanopatterned monolayer graphene (NPG). Most importantly, the LSPs along with an optical cavity increase the absorbance from about $N\times 2.6$\% for $N$-layer graphene-FeCl$_3$ (without patterning) to nearly 100\% for NPMLG-FeCl$_3$, where the strong absorbance occurs locally inside the graphene sheets only. Our NIR and SWIR detection scheme relies on the photo-thermoelectric effect induced by asymmetric patterning of the multi-layer graphene (MLG) sheets. The LSPs on the nanopatterned side create hot carriers that give rise to Seebeck photodetection at room temperature achieving a responsivity of $R=6.15\times 10^3$ V/W, a detectivity of $D^*=2.3\times 10^{9}$ Jones, and an ultrafast response time of the order of 100 ns. Our theoretical results pave the way to graphene-based photodetection, optical IR communication, IR color displays, and IR spectroscopy in the NIR, SWIR, mid-wavelength infrared (MWIR), and long-wavelength infrared (LWIR) regimes.