Substrate Sensitive Mid-Infrared Photoresponse in Graphene

TL;DR

This study investigates how substrate interactions influence mid-infrared photoresponse in graphene nanoribbons, revealing tunable hybrid polaritonic modes and substrate phonon effects that can optimize graphene photodetectors.

Contribution

It demonstrates substrate-dependent tunability of graphene's mid-IR photoresponse through hybrid polaritonic modes and substrate phonon interactions.

Findings

Hybrid polaritonic modes produce tunable thermal photocurrent.

Substrate phonon-polaritons induce fixed spectral photocurrent.

Responsivity can be tailored by substrate choice.

Abstract

We report mid-infrared photocurrent spectra of graphene nanoribbon arrays on SiO2 dielectrics showing dual signatures of the substrate interaction. First, hybrid polaritonic modes of graphene plasmons and dielectric surface polar phonons produce a thermal photocurrent in graphene with spectral features that are tunable by gate voltage, nanoribbon width, and light polarization. Secondly, phonon-polaritons associated with the substrate are excited, which indirectly heat up the graphene leading to a graphene photocurrent with fixed spectral features. Models for other commonly used substrates show that the responsivity of graphene infrared photodetectors can be tailored to specific mid-IR frequency bands by the choice of the substrate.