Photocurrent imaging and efficient photon detection in a graphene transistor

TL;DR

This paper uses scanning photocurrent imaging to analyze the potential profile in graphene transistors, revealing how metal contacts influence the channel and demonstrating efficient photon detection with high responsivity.

Contribution

It introduces a method to map channel potential in graphene transistors and shows how metal contacts affect the entire channel, along with achieving high responsivity in photon detection.

Findings

Metal influence extends over 1/3 of the channel length.

Potential barrier varies with gate bias.

Responsivity of 0.001 A/W achieved at p-n junctions.

Abstract

We measure the channel potential of a graphene transistor using a scanning photocurrent imaging technique. We show that at a certain gate bias, the impact of the metal on the channel potential profile extends into the channel for more than 1/3 of the total channel length from both source and drain sides, hence most of the channel is affected by the metal. The potential barrier between the metal controlled graphene and bulk graphene channel is also measured at various gate biases. As the gate bias exceeds the Dirac point voltage, VDirac, the original p-type graphene channel turns into a p-n-p channel. When light is focused on the p-n junctions, an impressive external responsivity of 0.001 A/W is achieved, given that only a single layer of atoms are involved in photon detection.