Plasmon resonant amplification of a hot electron-driven photodiode

摘要

We report plasmon resonant excitation of hot electrons in a photodetector based on 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 with a pitch of 500 nm.The photocurrent produced in this device is measured using 633-nm-wavelength light as a function of incident angle.We observe the maximum photocurrent at ±10° from normal incidence under irradiation with light polarized parallel to the incident plane (p-polarizafion) and perpendicular to the lines on the grating,and a constant (angle-independent) photocurrent under irradiation with light polarized perpendicular to the incident plane (s-polarization) and 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 waveve ctor matching between the incident light and the plasmon mode in the grating.In addition,finite-difference time-domain simulations predict sharp dips in the photoreflectance at ±10°,and the electric field intensity profiles show clear excitation of a plasmon resonant mode when illuminated with p-polarized light at this angle.