Hot Carrier-Assisted Intrinsic Photoresponse in Graphene

TL;DR

This paper reveals that hot-carrier transport, rather than photovoltaic effects, primarily drives the intrinsic photoresponse in high-quality graphene p-n junctions, highlighting a novel energy transport regime with potential optoelectronic applications.

Contribution

The study demonstrates that hot-carrier transport dominates the photoresponse in graphene p-n junctions, providing new insights into graphene's optoelectronic mechanisms.

Findings

Hot-carrier transport is the main mechanism behind the photoresponse.

Six-fold photovoltage patterns indicate hot-carrier dominance.

Long-lived hot carriers enable efficient energy transport at the nanoscale.

Abstract

Graphene is a new material showing high promise in optoelectronics, photonics, and energy-harvesting applications. However, the underlying physical mechanism of optoelectronic response has not been established. Here, we report on the intrinsic optoelectronic response of high-quality dual-gated monolayer and bilayer graphene p-n junction devices. Local laser excitation at the p-n interface leads to striking six-fold photovoltage patterns as a function of bottom- and top-gate voltages. These patterns, together with the measured spatial and density dependence of the photoresponse, provide strong evidence that non-local hot-carrier transport, rather than the photovoltaic effect, dominates the intrinsic photoresponse in graphene. This novel regime, which features a long-lived and spatially distributed hot carrier population, may open the doorway for optoelectronic technologies exploiting efficient energy transport at the nanoscale.