Carrier transport in 2D graphene layers

TL;DR

This paper presents a theoretical analysis of carrier transport in 2D graphene layers, showing excellent agreement with experiments and explaining key phenomena such as conductivity asymmetry and saturation.

Contribution

It provides a comprehensive theoretical model for graphene conductivity considering charged impurity scattering, matching experimental data and explaining observed asymmetries and saturation effects.

Findings

Conductivity scales linearly with carrier density over impurity density.

Weak temperature dependence of conductivity.

Saturation of conductivity at low density explained by impurity-induced inhomogeneity.

Abstract

Carrier transport in gated 2D graphene monolayers is theoretically considered in the presence of scattering by random charged impurity centers with density $n_i$. Excellent quantitative agreement is obtained (for carrier density $n > 10^{12} \rm{cm}^{-2}$) with existing experimental data (Ref. \onlinecite{kn:novoselov2004, kn:novoselov2005, kn:zhang2005, kn:kim2006, kn:fuhrer2006}). The conductivity scales linearly with $n/n_i$ in the theory, and shows extremely weak temperature dependence. The experimentally observed asymmetry between electron and hole conductivities is explained by the asymmetry in the charged impurity configuration in the presence of the gate voltage, while the high-density saturation of conductivity for the highest mobility samples is explained as a crossover between the long-range and the point scattering dominated regimes. We argue that the experimentally observed saturation of conductivity at low density arises from the charged impurity induced inhomogeneity in the graphene carrier density which becomes severe for $n \lesssim n_i \sim 10^{12} \rm{cm}^{-2}$.