Optimization of source/drain doping level of carbon nanotube field-effect transistors to suppress OFF-state leakage current while keeping ideal ON-state current

Berrin Pinar Algul, Ken Uchida

Research output: Contribution to journalArticle

Abstract

The effects of doping concentration variation in source/drain junctions on the characteristics of carbon nanotube field-effect transistors (CNFETs) have been studied in order to realize high performance CNFETs, where suppressed OFF-state leakage current and ideal maximum ON-state current were obtained. The characteristics of CNFETs with doped source/drain regions have been studied by solving the Poisson and carrier transport equations self-consistently. The transmission coefficient through the bandgap (E g) has been calculated using the Wentzel-Kramers-Brillouin (WK B) approximation in order to take into account the band-to-band tunneling (BTBT) leakage current. The doping is characterized by the Fermi level (E d) in a doped region which is measured from the conduction band edge. In this study, it is demonstrated that, when the power supply voltage (V dd) is greater than the bandgap of carbon nanotubes (CNTs), optimized doping level E d of V dd - E g shows the lowest OFF-state current (IOFF). On the other hand, when V dd is smaller than E g, IOFF monotonically decreases as Ed decreases, although the aggressively lowered doping concentration results in lower ON-state current. We also demonstrated that CNFETs with low source/drain doping concentration exhibit current saturation at higher gate voltages. The current saturation results from the fact that the injection velocity to the channel is limited by the velocity in the source region which is determined by the source doping level. We showed that, in order to avoid the current saturation, doping level should be higher than 0.3 eV, regardless of carbon nanotube diameter.

Original languageEnglish
Article number06FD27
JournalJapanese Journal of Applied Physics
Volume51
Issue number6 PART 2
DOIs
Publication statusPublished - 2012 Jun
Externally publishedYes

Fingerprint

Carbon nanotube field effect transistors
Leakage currents
leakage
field effect transistors
carbon nanotubes
Doping (additives)
optimization
saturation
Carbon nanotubes
Energy gap
Carrier transport
Electric potential
Fermi level
Conduction bands
electric potential
power supplies
conduction bands
injection

ASJC Scopus subject areas

  • Engineering(all)
  • Physics and Astronomy(all)

Cite this

Optimization of source/drain doping level of carbon nanotube field-effect transistors to suppress OFF-state leakage current while keeping ideal ON-state current. / Algul, Berrin Pinar; Uchida, Ken.

In: Japanese Journal of Applied Physics, Vol. 51, No. 6 PART 2, 06FD27, 06.2012.

Research output: Contribution to journalArticle

@article{c90829d1db824eb49f65c3b8ec13f00d,
title = "Optimization of source/drain doping level of carbon nanotube field-effect transistors to suppress OFF-state leakage current while keeping ideal ON-state current",
abstract = "The effects of doping concentration variation in source/drain junctions on the characteristics of carbon nanotube field-effect transistors (CNFETs) have been studied in order to realize high performance CNFETs, where suppressed OFF-state leakage current and ideal maximum ON-state current were obtained. The characteristics of CNFETs with doped source/drain regions have been studied by solving the Poisson and carrier transport equations self-consistently. The transmission coefficient through the bandgap (E g) has been calculated using the Wentzel-Kramers-Brillouin (WK B) approximation in order to take into account the band-to-band tunneling (BTBT) leakage current. The doping is characterized by the Fermi level (E d) in a doped region which is measured from the conduction band edge. In this study, it is demonstrated that, when the power supply voltage (V dd) is greater than the bandgap of carbon nanotubes (CNTs), optimized doping level E d of V dd - E g shows the lowest OFF-state current (IOFF). On the other hand, when V dd is smaller than E g, IOFF monotonically decreases as Ed decreases, although the aggressively lowered doping concentration results in lower ON-state current. We also demonstrated that CNFETs with low source/drain doping concentration exhibit current saturation at higher gate voltages. The current saturation results from the fact that the injection velocity to the channel is limited by the velocity in the source region which is determined by the source doping level. We showed that, in order to avoid the current saturation, doping level should be higher than 0.3 eV, regardless of carbon nanotube diameter.",
author = "Algul, {Berrin Pinar} and Ken Uchida",
year = "2012",
month = "6",
doi = "10.1143/JJAP.51.06FD27",
language = "English",
volume = "51",
journal = "Japanese Journal of Applied Physics, Part 1: Regular Papers & Short Notes",
issn = "0021-4922",
publisher = "Japan Society of Applied Physics",
number = "6 PART 2",

}

TY - JOUR

T1 - Optimization of source/drain doping level of carbon nanotube field-effect transistors to suppress OFF-state leakage current while keeping ideal ON-state current

AU - Algul, Berrin Pinar

AU - Uchida, Ken

PY - 2012/6

Y1 - 2012/6

N2 - The effects of doping concentration variation in source/drain junctions on the characteristics of carbon nanotube field-effect transistors (CNFETs) have been studied in order to realize high performance CNFETs, where suppressed OFF-state leakage current and ideal maximum ON-state current were obtained. The characteristics of CNFETs with doped source/drain regions have been studied by solving the Poisson and carrier transport equations self-consistently. The transmission coefficient through the bandgap (E g) has been calculated using the Wentzel-Kramers-Brillouin (WK B) approximation in order to take into account the band-to-band tunneling (BTBT) leakage current. The doping is characterized by the Fermi level (E d) in a doped region which is measured from the conduction band edge. In this study, it is demonstrated that, when the power supply voltage (V dd) is greater than the bandgap of carbon nanotubes (CNTs), optimized doping level E d of V dd - E g shows the lowest OFF-state current (IOFF). On the other hand, when V dd is smaller than E g, IOFF monotonically decreases as Ed decreases, although the aggressively lowered doping concentration results in lower ON-state current. We also demonstrated that CNFETs with low source/drain doping concentration exhibit current saturation at higher gate voltages. The current saturation results from the fact that the injection velocity to the channel is limited by the velocity in the source region which is determined by the source doping level. We showed that, in order to avoid the current saturation, doping level should be higher than 0.3 eV, regardless of carbon nanotube diameter.

AB - The effects of doping concentration variation in source/drain junctions on the characteristics of carbon nanotube field-effect transistors (CNFETs) have been studied in order to realize high performance CNFETs, where suppressed OFF-state leakage current and ideal maximum ON-state current were obtained. The characteristics of CNFETs with doped source/drain regions have been studied by solving the Poisson and carrier transport equations self-consistently. The transmission coefficient through the bandgap (E g) has been calculated using the Wentzel-Kramers-Brillouin (WK B) approximation in order to take into account the band-to-band tunneling (BTBT) leakage current. The doping is characterized by the Fermi level (E d) in a doped region which is measured from the conduction band edge. In this study, it is demonstrated that, when the power supply voltage (V dd) is greater than the bandgap of carbon nanotubes (CNTs), optimized doping level E d of V dd - E g shows the lowest OFF-state current (IOFF). On the other hand, when V dd is smaller than E g, IOFF monotonically decreases as Ed decreases, although the aggressively lowered doping concentration results in lower ON-state current. We also demonstrated that CNFETs with low source/drain doping concentration exhibit current saturation at higher gate voltages. The current saturation results from the fact that the injection velocity to the channel is limited by the velocity in the source region which is determined by the source doping level. We showed that, in order to avoid the current saturation, doping level should be higher than 0.3 eV, regardless of carbon nanotube diameter.

UR - http://www.scopus.com/inward/record.url?scp=84863309148&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84863309148&partnerID=8YFLogxK

U2 - 10.1143/JJAP.51.06FD27

DO - 10.1143/JJAP.51.06FD27

M3 - Article

VL - 51

JO - Japanese Journal of Applied Physics, Part 1: Regular Papers & Short Notes

JF - Japanese Journal of Applied Physics, Part 1: Regular Papers & Short Notes

SN - 0021-4922

IS - 6 PART 2

M1 - 06FD27

ER -