Evidence for Extraction of Photoexcited Hot Carriers from Graphene

TL;DR

This paper provides experimental evidence of hot carrier extraction from graphene using gate-dependent photocurrent measurements, revealing unique behaviors under femtosecond laser excitation and highlighting potential for graphene-based hot carrier optoelectronic devices.

Contribution

The study demonstrates direct evidence of nonequilibrium hot carrier extraction from graphene and explores its dependence on gate voltage and excitation conditions.

Findings

Hot carriers are efficiently extracted near the Dirac point.

Gate-dependent photocurrent shows unusual behavior with femtosecond laser excitation.

Hot carrier extraction is confirmed through power dependence studies.

Abstract

We report evidence of nonequilibrium hot carriers extraction from graphene by gate-dependent photocurrent study. Scanning photocurrent excited by femtosecond pulse laser shows unusual gate dependence compared with continuous wave (CW) laser excitation. Power dependence studies further confirm that the photocarriers extracted at the metal/graphene contact are nonequilibrium hot carriers. Hot carrier extraction is found to be most efficient near the Dirac point where carrier lifetime reaches maximum. These observations not only provide evidence of hot carrier extraction from graphene, but also open the door for graphene based hot carrier optoelectronics.