Plasmon-enhanced graphene photodetector with CMOS-compatible titanium nitride

Graphene has emerged as an ultrafast optoelectronic material for on-chip photodetector applications. The 2D nature of graphene enables its facile integration with complementary metal-oxide semiconductor (CMOS) microelectronics and silicon photonics, yet graphene absorbs only $\sim$2.3% of light. Plasmonic metals can enhance the responsivity of graphene photodetectors, but may result in CMOS-incompatible devices, depending on the choice of metal. Here, we propose a plasmon-enhanced photothermoelectric graphene detector using CMOS-compatible titanium nitride (TiN) on the silicon-on-insulator (SOI) platform. The device performance is quantified by its responsivity, operation speed, and noise equivalent power. Its bandwidth exceeds 100$\,$GHz, and it exhibits a nearly flat photoresponse across the telecom C-band. The photodetector responsivity is as high as 1.4$\,$A/W (1.1$\,$A/W external) at an ultra-compact length of 3.5$\,\mu$m, which is the most compact footprint reported for a graphene-based waveguide photodetector. Furthermore, it operates at zero-bias, consumes zero energy, and has an ultra-low intrinsic noise equivalent power (NEP$\,$<$\,25\:\text{pW/}\sqrt{\text{Hz}}$)