Modeling of the Output and Transfer Characteristics of Graphene Field-Effect Transistors

We obtain the output and transfer characteristics of graphene field-effect transistors by using the charge-control model for the current, based on the solution of the Boltzmann equation in the field-dependent relaxation time approximation. Closed expressions for the conductance, transconductance and saturation voltage are derived. We found good agreement with the experimental data of Meric et al. [Nature Nanotechnology 3, 684 (2008)] without assuming carrier density-dependent velocity saturation.Comment: 7 pages, 8 figure

High field electro-thermal transport in metallic carbon nanotubes

We describe the electro-thermal transport in metallic carbon nanotubes (m-CNTs) by a semi-classical approach that takes into account the high-field dynamical interdependence between charge carrier and phonon populations. Our model is based on the self-consistent solution of the Boltzmann transport equation and the heat equation mediated by a phonon rate equation that accounts for the onset of non-equilibrium (optical) phonons in the high-field regime. Given the metallic nature of the nanostructures, a key ingredient of the model is the assumption of local thermalization of charge carriers. Our theory remarkably reproduces the room temperature electrical characteristics of m-CNTs on substrate and free standing (suspended), shedding light on charge-heat transport in these one dimensional nanostructures. In particular, the negative differential resistance observed in suspended m-CNTs under electric stress is attributed to inhomogeneous field profile induced by self-heating rather than the presence of hot phonons.Comment: 10 pages, 10 figure

Restricted Wiedemann-Franz law and vanishing thermoelectric power in one-dimensional conductors

In one-dimensional (1D) conductors with linear E-k dispersion (Dirac systems) intrabranch thermalization is favored by elastic electron-electron interaction in contrast to electron systems with a nonlinear (parabolic) dispersion. We show that under external electric fields or thermal gradients the carrier populations of different branches, treated as Fermi gases, have different temperatures as a consequence of self-consistent carrier-heat transport. Specifically, in the presence of elastic phonon scattering, the Wiedemann-Franz law is restricted to each branch with its specific temperature and is characterized by twice the Lorenz number. In addition thermoelectric power vanishes due to electron-hole symmetry, which is validated by experiment.Comment: 10 pages, 2 figure