Carrier Transport in Two-Dimensional Graphene Layers

TLDR

Carrier transport in gated two‑dimensional graphene monolayers is studied in the presence of scattering by random charged impurity centers of density \(n_i\). The theory achieves excellent agreement with experiment for carrier densities above \(10^{12}\,\text{cm}^{-2}\), predicts a linear scaling of conductivity with \(n/n_i\), explains electron–hole asymmetry and high‑density saturation, and attributes low‑density saturation to charged‑impurity‑induced carrier‑density inhomogeneity.

Abstract

Carrier transport in gated 2D graphene monolayers is considered in the presence of scattering by random charged impurity centers with density ${n}_{i}$. Excellent quantitative agreement is obtained (for carrier density $n>{10}^{12}\text{ }\text{ }{\mathrm{cm}}^{\ensuremath{-}2}$) with existing experimental data. The conductivity scales linearly with $n/{n}_{i}$ in the theory. We explain the experimentally observed asymmetry between electron and hole conductivities, and the high-density saturation of conductivity for the highest mobility samples. 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 $n\ensuremath{\lesssim}{n}_{i}\ensuremath{\sim}{10}^{12}\text{ }\text{ }{\mathrm{cm}}^{\ensuremath{-}2}$.