Ultrafast Plasmonic Graphene Photodetector Based on the Channel Photothermoelectric Effect

We propose an ultrafast on-chip CMOS compatible graphene plasmonic photodetector based on the photothermoelectric effect (PTE) that occurs across an entire homogeneous graphene channel and operating beyond 500 GHz. The proposed photodetector incorporates the long-range dielectric-loaded surface plasmon polariton (LR-DLSPP) waveguide with a metal stripe serving simultaneously as a plasmon supporting metallic material and one of the metal electrodes. The large in-plane component of the transverse magnetic (TM) plasmonic mode can couple efficiently to the graphene causing large electron temperature increases across an entire graphene channel with a maximum located at the metal stripe edge. As a result, the electronic temperatures exceeding 6000 K at input power of only a few tens of μW can be obtained at the telecom wavelength of 1550 nm. Even with limitations such as the melting temperature of graphene (T = 4510 K), a responsivity exceeding at least 200 A/W is achievable at a telecom wavelength of 1550 nm. It is also shown that, under certain operation conditions, the PTE channel photocurrent can be isolated from photovoltaic and p-n junction PTE contributions providing an efficient way for optimizing the overall photodetector performance.