Method for determining the residual electron- and hole- densities about the neutrality point over the gate-controlled n $\leftrightarrow$ p transition in graphene

TL;DR

This paper investigates residual electron and hole densities in CVD graphene near the neutrality point, using Hall effect measurements and modeling to understand mixed ambipolar transport during the n to p transition.

Contribution

It introduces a method combining Hall effect data and a neutrality potential distribution model to quantify residual charge carrier densities in graphene.

Findings

Residual resistivity approximately h/4e^2 observed.

Mixed electron-hole transport confirmed near neutrality point.

Domain-confined ambipolar currents dominate during n-p transition.

Abstract

The Hall effect, and the diagonal resistance, which indicates a residual resistivity $\rho_{xx} \approx h/4e^{2}$, are experimentally examined over the p$\leftrightarrow$n transition about the nominal neutrality point in chemical vapor deposition (CVD) grown graphene. A distribution of neutrality potentials is invoked in conjunction with multi-carrier conduction to model the experimental observations. From the modeling, we extract the effective residual electron- and hole- densities around the nominal neutrality point. The results indicate mixed transport due to co-existing electrons and holes in large area zero-band gap CVD graphene devices, which indicates domain confined ambipolar currents broadly over the gate-induced n $\leftrightarrow$ p transition.