Comparing Carbon Nanotube Transistors—The Ideal Choice: A Novel Tunneling Device Design

Abstract

Abstract-Three different carbon nanotube (CN) field-effect transistor (CNFET) designs are compared by simulation and experiment. While a C-CNFET with a doping profile similar to a "conventional" (referred to as C-CNFET in the following) p-or n-MOSFET in principle exhibits superior device characteristics when compared with a Schottky barrier CNFET, we find that aggressively scaled C-CNFET devices suffer from "charge pile-up" in the channel. This effect which is also known to occur in floating body silicon transistors deteriorates the C-CNFET off-state substantially and ultimately limits the achievable on/off-current ratio. In order to overcome this obstacle we explore the possibility of using CNs as gate-controlled tunneling devices (T-CNFETs). The T-CNFET benefits from a steep inverse subthreshold slope and a well controlled off-state while at the same time delivering high performance on-state characteristics. According to our simulation, the T-CNFET is the ideal transistor design for an ultrathin body three-terminal device like the CNFET. Index Terms-Carbon nanotube (CN), field-effect transistor (FET), tunneling (T) device.

Influence of phonon scattering on the performance of p-i-n band-to-band tunneling transistors

“…25,27 Here, we examine another popular tunneling device structure based on gated p-i-n geometry ͑p-i-n TFET͒. [2][3][4][5]7,15,16 The purpose of this letter is to examine how phonon scattering affects the performance of such devices. Although we use the CNT as a model device, the general conclusions are expected to be broadly applicable to this class of devices fabricated in different materials.…”

Device Simulation of SWNT-FETs

“…The barrier is thin when the gate oxide is thin, and it is nearly transparent for any physical value of the SB height. Although the hole conduction current is larger than the elctron conduction current for a CNT SBFET with a zero SB height for holes, the transistor still qualitatively shows ambipolar characteristics when the oxide is thin (<10nm) [5,29].…”

“…The results indicate that it is important to treat phononassisted scattering in order to accurately compute the minimal leakage current. The steep subthreshold slope in the band-to-band tunneling current promises a new type of transistor with a subthreshold swing less than 60mV/dec [5]. Phonon-assisted tunneling again plays an important role on determining the exact value of the subthreshold slope for the band-to-band tunneling current.…”

“…Device simulations of CNTFETs have been extensively reported in last five years [5][6][7][8][9][10][11][12][13][14][15][16]. Significant advances have been achieved in developing simulation methods, understanding device physics, and optimizing designs using modeling and simulation.…”

Issues in the modeling of carbon nanotube FETs: Structure, gate thickness, and azimuthal asymmetry

“…For illustrative purposes, we examine the p-i-n doped-contact CNFET. This device is of particular interest because it appears capable of an exceptional sub-threshold slope [1]. We self-consistently solve the equations of Poisson and Schrödinger: the latter gives the local density of states from a p z -tight-binding Hamiltonian using a Green's Function 1 approach, within which the self-energies for the semi-infinite leads are computed by solving a quadratic matrix equation [3].…”