Flexural-Phonon Scattering Induced by Electrostatic Gating in Graphene

Abstract

Graphene has an extremely high carrier mobility partly due to its planar mirror symmetry inhibiting scattering by the highly occupied acoustic flexural phonons. Electrostatic gating of a graphene device can break the planar mirror symmetry yielding a coupling mechanism to the flexural phonons. We examine the effect of the gate-induced one-phonon scattering on the mobility for several gate geometries and dielectric environments using first-principles calculations based on density functional theory (DFT) and the Boltzmann equation. We demonstrate that this scattering mechanism can be a mobility-limiting factor, and show how the carrier density and temperature scaling of the mobility depends on the electrostatic environment. Our findings may explain the high deformation potential for in-plane acoustic phonons extracted from experiments and furthermore suggest a direct relation between device symmetry and resulting mobility.

Density functional perturbation theory for gated two-dimensional heterostructures: Theoretical developments and application to flexural phonons in graphene

“…(2) of Ref. 23, the authors considered a deformation potential (called "field-induced coupling constant") that depends on gate-voltage but is independent of momentum q. The screening from the conduction electrons of graphene does in fact bring a strong momentum dependency 9 to this quantity.…”

“…Those FET-specific effects have not been studied in the context of DFPT. The electron-phonon coupling with flexural phonons in gated graphene was recently studied by first-principles and suggested to be a significant scattering mechanism 23 . However, in this work, the calculations performed do not completely include the effect of metallic screening on the electron-phonon coupling.…”

“…Furthermore, the method used in Ref. 23 assumes the Fourier transform of the derivative of the self-consistent potential to be phonon-momentum independent. We will show that this is not the case in doped graphene.…”

“…In isolated graphene, those phonons do not couple to electrons due the mirror symmetry with respect to the graphene plane 22 . In a FET setup, however, this symmetry is broken and flexural phonons have recently been suggested 23 as a significant scattering mechanism in transport measurements. We recover the expected result that a symmetry-breaking electric field can activate a significant bare electron-phonon interaction with flexural phonons.…”

First-principles electron transport with phonon coupling: Large scale at low cost

“…However, in between these two regimes efficient computational methods are missing. One approach is to apply the continuum DP, despite the fact that electron-phonon coupling (EPC) is known to change significantly in nanostructured devices [18][19][20] and in an electrostatic environment [21]. Alternatively, it is possible to perform atomistic tight-binding calculations with coarse diagonal self-energy approximations at an extensive computational cost [22,23].…”