Conductance of p-n-p graphene structures with 'air-bridge' top gates

TL;DR

This paper reports on the fabrication and analysis of graphene p-n-p structures with air-bridge top gates, demonstrating how chiral carrier transmission affects junction resistance.

Contribution

It introduces a novel air-bridge top gate design for graphene, enabling study of chiral carrier transport without reducing mobility.

Findings

Ballistic p-n junctions exhibit higher resistance than diffusive ones.

Chiral carrier transmission is suppressed at non-normal angles, increasing resistance.

Theoretical calculations match experimental resistance measurements.

Abstract

We have fabricated graphene devices with a top gate separated from the graphene layer by an air gap--a design which does not decrease the mobility of charge carriers under the gate. This gate is used to realise p-n-p structures where the conducting properties of chiral carriers are studied. The band profile of the structures is calculated taking into account the specifics of the graphene density of states and is used to find the resistance of the p-n junctions expected for chiral carriers. We show that ballistic p-n junctions have larger resistance than diffusive ones. This is caused by suppressed transmission of chiral carriers at angles away from the normal to the junction.