Hot-carrier assisted Photo-thermoelectric current using nano-plasmonic structures in GFET

Based on Photo-thermoelectric effect, by illuminating the active area of graphene-based optoelectronic devices, strong electron-electron interactions of the photo-excited carriers along with inherit inefficiency of electron-lattice energy relaxation in graphene, results in a sustained population of hot carriers. Furthermore, according to this effect, using generated hot-carrier temperature profile and thermoelectric power(S)coefficient, produce a net photo-thermoelectric current via the thermoelectric effect. The weakness point of this scenario is optical absorption of graphene. A promising solution to overcome this problem is using plasmonic nanostructures. Here, we show that by using a series of periodic plasmonic grating on top of electrodes, a considerable tunable asymmetry hot carrier profile on the graphene channel can be created. It is shown that by precise design of grating there would be a strong field distribution along one side of graphene sheet, which leads to an increased efficiency and responsivity of graphene-based photodetector. The calculated photo-thermoelectric current (ITEP ) shows 6-fold pattern which is qualitatively similar to photo-thermoelectric patterns in experimental results.