Photocurrent in a visible-light graphene photodiode

TL;DR

This paper theoretically analyzes the photocurrent generated in a graphene photodiode under visible light, focusing on resonant photon absorption and its dependence on photon energy, polarization, and electrostatic potential.

Contribution

It provides a detailed calculation of photocurrent in graphene under high photon energies, highlighting the effects of polarization and potential barriers, relevant for photodetector design.

Findings

Photocurrent decreases as photon energy exceeds potential barrier height.

Photocurrent is weakly affected by background gate voltage.

Photocurrent depends on light polarization as sin^2(γ).

Abstract

We calculate the photocurrent in a clean graphene sample normally irradiated by a monochromatic electromagnetic field and subject to a step-like electrostatic potential. We consider the photon energies $\hbar\Omega$ that significantly exceed the height of the potential barrier, as is the case in the recent experiments with graphene-based photodetectors. The photocurrent comes from the resonant absorption of photons by electrons and decreases with increasing ratio $\hbar\Omega/U_0$. It is weakly affected by the background gate voltage and depends on the light polarization as $\propto\sin^2\gamma$, $\gamma$ being the angle between the potential and the polarization plane.