Enhanced Spectrally Selective Terahertz Detection in a Photo-Thermoelectric Graphene Detector With Dual Nano-Grating Gates

We introduce a high-performance terahertz detector based on the photo-thermoelectric effect (PTE) in graphene. Our study outlines a novel approach to enhance terahertz detection through a photodetector that employs a hybrid structure. This structure combines the localized surface plasmon resonance of dual grating gates with the resonant modes of a Fabry-Perot cavity configuration, facilitating a strong interaction between terahertz light and the active graphene layer, thereby improving light absorption. Our numerical investigation reveals frequency selectivity within the terahertz absorptance spectrum for incident waves with transverse magnetic polarization, leading to near-perfect absorptance of graphene. This substantial absorption creates an amplified thermal gradient across the graphene channel due to localized heat generation from terahertz wave absorption. The detector’s absorption characteristics can be adjusted by altering geometrical parameters and tuning two gate voltages. Furthermore, incorporating dual grating gates to create a pn-junction leads to a non-uniform Seebeck coefficient along the channel, enhancing the generated voltage. At a resonant frequency of 1.6 THz, the detector demonstrates a responsivity of 1.26 V/W and a noise-equivalent power (NEP) of $5.2 \mathrm {nW}/\sqrt {\mathrm {Hz}}$ at room temperature, under biasing the two grating gates with the low voltages of ±0.2 V.