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We investigate the electrical transport characteristics of graphene channel field-effect transistors (FETs) gated via ionic solid (IS), where the conventional gate insulator, such as SiO 2 , has been replaced by solid electrolytes, such as LiP 3 O 4. In this study, we focus on (i) the gate controllability of the current in comparison to conventional graphene FETs with SiO 2 as an insulating material and (ii) the transient characteristics of the drain current and time required to switch on the current. We employ the tight-binding formalism and Boltzmann equation to calculate the electronic band structure and the electronic transport in graphene, while the Nernst–Planck–Poisson equations have been employed to calculate the time-dependent charge distribution in solid electrolytes and the resulting electric double layer formation at the graphene/IS and IS/gate interfaces. Our simulations have shown that graphene FET gated via IS shows superior gate controllability more than SiO 2 -gated graphene FET with the insulator thickness of 1 nm, and the saturated drain current is insensitive to the IS thickness. Moreover, the time required to switch on the drain current is proportional to the thickness of IS, and the limited number of Li + ion vacancies in IS is preferable in obtaining faster switching than the case of unlimited vacancy cases while keeping the superior gate controllability. [ABSTRACT FROM AUTHOR]

We present a numerical study on the impact of electron–phonon scattering on the performance of a strained-graphene field-effect transistor, where the Dirac point of the channel region is shifted along the transverse momentum direction by a strain-induced vector potential and a high on-current/off-current (I on / I off ) ratio as well as a subthreshold slope (SS) steeper than 60 mV/dec have been predicted in the absence of the electron–phonon interaction previously. By using the Dirac-type effective Hamiltonian description for strained graphene and the non-equilibrium Green's function method to systematically account for the electron–phonon scattering, along with Poisson's equation, we demonstrate that the abovementioned I on / I off ratio and SS value can be maintained even in the presence of electron–phonon scattering, although the I on / I off ratio and the I D range over which the steep SS persists are reduced. [ABSTRACT FROM AUTHOR]

A self-consistent and 3-dimensional (3-D) quantum simulator is described for Si-nanowire transistors based on the Wigner function model and multidimensional Schrodinger-Poisson algorithm. The studies have shown that the source-drain tunneling is a major phenomenon related to a scaling limit of nanowire devices, and the semiclassical simulation has measurably underestimated a minimum gate length.

A comparative computational study on the strain effects in Si nanostructures including bulk, thin film and nanowire configurations is described. First principles calculation is used for identifying the bandstructure parameters such as band splitting energy and transport effective mass and it is shown that bulk Si and Si thin films have similar strain effects on the bandstructure parameters under uniaxial strain.

The linear and nonlinear characteristics of electron waveguides with respect to ionized impurity scattering are investigated through the Wigner function model. The waveguides' pertinent parameters and transition probability caused by impurity scattering are represented by using the one-dimensional Liouville equation and the transverse eigenfunctions. Results show that the waveguides' quantized steps of conductance deteriorate with the increase in the total amount of impurities.

Graphene nanomeshes (GNMs) are expected to be a high-performance channel material for metal-oxide-semiconductor field-effect-transistors (MOSFETs), since they can open up a band gap in a large sheet of graphene thin film by simply introducing two-dimensional periodical nanoscale holes. In this paper, we theoretically investigate the electronic band structures and the electron transport properties of GNMs based on a tight-binding approach. We demonstrate that GNMs have the capability of band structure engineering by controlling its neck width and furthermore the potential ability providing high current drivability when applied to a field-effect-transistor channel. [ABSTRACT FROM AUTHOR]

We have investigated the fundamental transport characteristics in carbon nanotubes (CNTs) in order to realize a high-frequency device. In the present analysis, the electron and hole densities are excited at each lead and propagate as a wave from the left contact to the right contact in the CNTs. First, we applied Green’s-function method formulation to CNTs with arbitrary chirality. We then calculated the basic conductive characteristics in the CNTs. In the metallic and intrinsic CNTs, the assumption of a linearly varying potential distribution is valid because the electron and hole densities satisfy the charge neutrality condition, and their distributions become uniform. We evaluated the I-V characteristics of semiconductive and metallic CNTs. Based on the obtained results, we can control the differential conductance from a negative value to a value of several times the conductance quantum by means of chirality, Fermi level, and bias voltage. We evaluated the GV/I-V characteristics of the zigzag CNT and found that when the group velocity of a mode with a real wave vector is comparable to that of another mode, GV/I takes a maximum at V0, which corresponds to the transition between these modes. [ABSTRACT FROM AUTHOR]

We have studied the basic conductive characteristics in carbon nanotubes (CNTs) for the purpose of application to a high-frequency device. In the analysis, the current flow in the CNTs is viewed as the quantum transport of electronic waves. First, we analyzed the dispersion relations of electronic waves in the CNTs based on the linear combination of atomic orbitals expansion method. In addition, we investigated the current-density distributions around the circumference of the CNTs and the current-voltage characteristics by using the transfer-matrix method. As a result, the current distributions were found to be significantly controlled by both the chirality of the CNTs and the position of the current sources around the circumference. Based on these results, we propose herein a ferrite device that acts as a filter in the terahertz frequency domain. In this device, the high-frequency current flowing on the CNTs may excite and receive directly the spin waves in the ferrite film beneath them, and the operating wavelength may be controlled by means of the chirality via the current-density distributions on the CNTs. In addition, we found that the performance of the device can be improved by using the p-type CNTs as the excitation electrodes rather than the intrinsic CNTs. [ABSTRACT FROM AUTHOR]