  We present a micrometer scale, on-chip integrated, plasmonic enhanced
graphene photodetector (GPD) for telecom wavelengths operating at zero dark
current. The GPD is designed and optimized to directly generate a photovoltage
and has an external responsivity~12.2V/W with a 3dB bandwidth~42GHz. We utilize
Au split-gates with a$\sim$100nm gap to electrostatically create a p-n-junction
and simultaneously guide a surface plasmon polariton gap-mode. This increases
light-graphene interaction and optical absorption and results in an increased
electronic temperature and steeper temperature gradient across the GPD channel.
This paves the way to compact, on-chip integrated, power-efficient graphene
based photodetectors for receivers in tele and datacom modules
