Graphene Field-Effect Transistors with High On/Off Current Ratio and Large Transport Band Gap at Room Temperature (original) (raw)
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2010 10th IEEE International Conference on Solid-State and Integrated Circuit Technology, 2010
In this work, we studied current transport in mono-, biand tri-layer graphene. We find that both the temperature and carrier density dependencies in monolayer and bi-/tri-layers are diametrically opposite. These difference can be understood by the different density-of-states and the additional screening of the electrical field of the substrate surface polar phonons in bi-layer/tri-layer graphenes. We also find that silicon nitride can provide uniform coverage of graphene in field-effect transistors while preserving the channel mobility. Using this insulator, we studied field-induced band-gap or band-overlap in graphene with various numbers of layers.
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2010 10th IEEE International Conference on Solid-State and Integrated Circuit Technology, 2010
During the last few years, graphene has gained remarkable attention in the device community. Graphene transistors are evolving at a rapid pace and graphene-based devices are considered as an option for a post-Si electronics. To assess whether graphene can meet the high expectations or not, the properties and specifics of this new material have to be analyzed carefully. The present paper provides an overview of the current status of graphene transistor development and reviews the prospects and problems of these devices.
Physica E: Low-dimensional Systems and Nanostructures, 2018
Tens of graphene transistors with nanoperforated channels and different channel lengths were fabricated at the wafer scale. The nanoholes have a central diameter of 20 nm and a period of 100 nm, the lengths of the channel being of 1, 2, 4 or 8 m. We have found that the mobility in these 2 m-wide transistors varies from about 10400 cm 2 /Vs for a channel length of 1 m to about 550 cm 2 /Vs for a channel length of 8 m. Irrespective of the mobility value, in all transistors the onoff ratio is in the range 10 3-10 4 at drain and gate voltages less than 2 V. The channel lengthdependent mobility and conductance values indicate the onset of strong localization of charge carriers, whereas the high on-off ratio is due to bandgap opening by nanoperforations.
Science, 2004
This review on graphene, a one-atom thick, two-dimensional sheet of carbon atoms, starts with a general description of the graphene electronic structure. The winning quality of graphene is a unique nature of charge carriers in graphene. Its charge carriers mimic relativistic particles and are easier and more natural to describe starting with the Dirac equation rather than the Schrodinger equation. This determines a number of unique phenomena observed in graphene, ranging from the absence of localization to new type of quantum Hall Effect (QHE). These exceptional properties make graphene a promising candidate for future electronic devices such as ballistic and single electron transistors, and spin-valve and ultra-sensitive gas sensors. The graphene transistor could play a role in post CMOS devices that are expected to be able to compute at much faster speeds than today's devices. Consequently, we explore the characteristics of graphene quantum dots, graphene field effect transistor for rf-applications, field emission from graphene nanoribbons transistor. Also, applications of graphene in the field of optoelectronics are explored in this review. Graphene may be promising for thermoelectric applications.
Graphene is a carbon allotrope in which the atoms are arranged in a two-dimensional honeycomb lattice, which comprises two hexagonal sublattices. The existence of these two sublattices gives rise to the electron pseudospin and, along with the overlapping pz orbitals, to the absence of back-scattering, which give to graphene high-quality transport properties. Graphene is a gapless material and currents in graphene nanoribbons cannot be effectively switched off. This is the most important obstacle for the use of graphene in the fabrication of integrated logic circuits. Recently, theoretical and experimental studies have shown that the conductance on graphene nanoribbons can be controlled in back and top gated graphene devices. Here we use tight-binding Hamiltonians and Non-equilibrium Green's Functions to design and simulate the operation of nanoelectronic graphene devices. We simulate the operation of the graphene FET (GFET), the graphene quantum-point contact and the potentially doped graphene p-n junction. Our results show that the conductance in these graphene devices can be tuned by the geometry of the device, and the top-gate and bottom-gate potentials. This conductance variation shows that graphene can be potentially used as the basic material for the forthcoming carbon based nanoelectronics.
Journal of Electronic Materials, 2019
The operation and performance of top-gated sub-100 nanometer graphene channel field-effect transistors were investigated. The device model is designed for graphene with a narrow energy band gap epitaxially grown on the SiC substrate. The issue of graphene-metallic lead coupling is appropriately taken into account. By assuming the graphene-metal physisorption contact, a self-consistent calculation reproduces two regions of high carrier density at the ends of the graphene channels underneath the metallic leads according to the charge transferred effect between the metallic lead surface and graphene. The charge carrier densities in these source and drain regions, however, are not pinned, but vary with respect to the drain and gate voltages. It is shown that, in general, the graphene channel supports the ambipolar characteristics for all device samples, but for the samples with the channels shorter than 40 nm, the current-voltage characteristic takes the exponential law. Particularly, the current saturation with a rather small output conductance of 126 S/m was observed in a sufficiently large range of drain voltage due to the dominance of the thermionic emission and conventional tunneling mechanisms to the bandto-band tunneling. A rough assessment of the device performance was also carried out. It reveals an extremely high cutoff frequency in the order of 10 3 GHz and a linear scaling rule for transistors with the channel length longer than 40 nm. The behaviour and magnitude of these quantities are consistent with an experimental study of sub-100 nm devices fabricated using the self-alignment technique.
Device model for graphene bilayer field-effect transistor
Journal of Applied Physics, 2009
We present an analytical device model for a graphene bilayer field-effect transistor (GBL-FET) with a graphene bilayer as a channel, and with back and top gates. The model accounts for the dependences of the electron and hole Fermi energies as well as energy gap in different sections of the channel on the bias back-gate and top-gate voltages. Using this model, we calculate the dc and ac source-drain currents and the transconductance of GBL-FETs with both ballistic and collision dominated electron transport as functions of structural parameters, the bias back-gate and top-gate voltages, and the signal frequency. It is shown that there are two threshold voltages, V th,1 and V th,2 , so that the dc current versus the top-gate voltage relation markedly changes depending on whether the section of the channel beneath the top gate (gated section) is filled with electrons, depleted, or filled with holes. The electron scattering leads to a decrease in the dc and ac currents and transconductances, whereas it weakly affects the threshold frequency. As demonstrated, the transient recharging of the gated section by holes can pronouncedly influence the ac transconductance resulting in its nonmonotonic frequency dependence with a maximum at fairly high frequencies.