Plasmon Resonant Amplification of a Hot Electron-Driven Photodiode*

In this talk I will review our recent progress in the area of plasmon resonant excitation of hot electrons in a metal/oxide/metal (Au/Al2O3/graphene) heterostructure. In this device, hot electrons, excited optically in the gold layer, jump over the oxide barrier and are injected into the graphene layer, producing a photocurrent. To amplify this process, the bottom gold electrode is patterned into a plasmon resonant grating structure. The photocurrent produced is measured as a function of incident angle. We observe the maximum photocurrent at ±10° from normal incidence with p-polarized light (perpendicular to grating lines), and a constant (angle-independent) photocurrent with s-polaried light (parallel to the grating). These data show an amplification factor of 4.6× under resonant conditions. At the same angle (±10°),we also observe sharp dips in the photoreflectance corresponding to wavevector matching between the incident light and the plasmon mode in the grating, in agreement with predictions from our FDTD simulations.