Pseudosaturation and Negative Differential Conductance in Graphene Field-Effect Transistors

Abstract

Abstract-We study theoretically the different transport behaviors and the electrical characteristics of a top-gated graphene field-effect transistor where boron nitride is used as the substrate and gate insulator material, which makes the ballistic transport realistic. Our simulation model is based on the Green's function approach to solving a tight-binding Hamiltonian for graphene, self-consistently coupled with Poisson's equation. The analysis emphasizes the effects of the chiral character of carriers in graphene in the different transport regimes including the Klein and band-to-band tunneling processes. In particular, the Klein tunneling is shown to have an important role on the onset of the current saturation which is analyzed in detail as a function of the device parameters. Additionally, we predict the possible emergence of negative differential conductance and investigate its dependence on the BN-induced bandgap, the temperature, and the gate insulator thickness. Short-channel effects are evaluated from the analysis of transfer characteristics as a function of gate length and gate insulator thickness. They manifest through the shift of the Dirac point and the appearance of current oscillations at short gate length.Index Terms-Dirac point, graphene field-effect transistor (GFET), negative differential conductance (NDC), short-channel effect.

Analysis of Graphene Tunnel Field-Effect Transistors for Analog/RF Applications

“…While, at small gate voltages, the quasi-linear increment in the current density is appeared for all V DS . The output characteristics of T-GFET is similar to the previous reports of short channel GFET [12], [13] as well as experimentally obtained GFET of long-channel GFET [4], [30].…”

“…3. For V GS = 0.6 V, a transmission valley, which separates current regimes in the current spectrum, is due to pseudoenergy gap by k y states around the channel potential energy, as evaluated in [12].…”

“…In addition, Alarcon et al [12] have recently observed that the source-to-channel (S-C) BTBT is responsible for the onset of current saturation in MOSFET like GFET, while the channel-to-drain (C-D) BTBT and the thermionic current dominance suppress saturation behavior. Interestingly, Ganapathi et al [13] have recently proposed that the current saturation in GFET can be improved by p-type doping in the drain underlap region to enhance the BTBT tunneling current dominance.…”

Conduction gap of strained/unstrained graphene junctions: Direction dependence

“…However, its applications are still limited because of the lack of bandgap between the valence and the conduction bands, which makes it very difficult to have a high ON/OFF current ratio and a good saturation of current in graphene transistors [1]. Many techniques to open the bandgap in graphene have been suggested such as cutting a graphene sheet into nanoribbons [2], applying an electric field perpendicular to a bilayer graphene sheet [3], removing periodically some carbon atoms on a pristine graphene sheet to create a nanohole lattice called graphene nanomesh [4,5] or even stacking graphene sheets on hexagonal boron nitride substrate [6].…”

Negative differential resistance in graphene nanoribbon superlattice field‐effect transistors

“…Work relating to three-terminal devices is rare. Alarcón et al [16] studied the NDR in wide graphene field effect transistors. That NDR was caused by doping, but in GNSL structures the NDR can be caused by the channel geometric shape's inhomogeneity.…”