Hot Carrier Transport and Photocurrent Response in Graphene

TL;DR

This paper demonstrates that in graphene, hot carriers generated by photon absorption significantly enhance photocurrent response, with quantum efficiencies exceeding unity due to inefficient electron cooling and hot-carrier transport.

Contribution

It reveals the role of hot carriers and carrier multiplication in graphene's photoresponse, highlighting the impact of electron cooling inefficiency on photocurrent.

Findings

Quantum efficiencies exceeding unity observed.

Photocurrent shows gate voltage dependence with sign changes.

Hot-carrier transport dominates energy transfer in graphene.

Abstract

Strong electron-electron interactions in graphene are expected to result in multiple-excitation generation by the absorption of a single photon. We show that the impact of carrier multiplication on photocurrent response is enhanced by very inefficient electron cooling, resulting in an abundance of hot carriers. The hot-carrier-mediated energy transport dominates the photoresponse and manifests itself in quantum efficiencies that can exceed unity, as well as in a characteristic dependence of the photocurrent on gate voltages. The pattern of multiple photocurrent sign changes as a function of gate voltage provides a fingerprint of hot-carrier-dominated transport and carrier multiplication.