Current Variability in Si Nanowire MOSFETs Due to Random Dopants in the Source/Drain Regions: A Fully 3-D NEGF Simulation Study

Seoane, Natalia; Martı́nez, Antonio; Brown, Andrew R.; Barker, John R.; Asenov, A.

doi:10.1109/ted.2009.2021357

Cited by 72 publications

(45 citation statements)

References 25 publications

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“…[3][4][5][6][7][8][9][10][11] However, its application area has gradually expanded over time to include electronic waveguides, 12 MOSFETs, [13][14][15] and semiconductor nanowires. [16][17][18] Although the non-equilibrium Green function (NEGF) method 4,16,19,20 is usually adopted for dealing with quantum transport problems nowadays, the Wigner function-based model or the Wigner transport equation (WTE) still remains as an attractive alternative in that it adopts a phase-space representation and allows an easy implementation of self-consistency with the Poisson equation.…”

Section: Introductionmentioning

confidence: 99%

An efficient numerical scheme for the discrete Wigner transport equation via the momentum domain narrowing

Kim

2016

AIP Advances

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We propose a numerical scheme that narrows down the momentum domain of the Wigner function to enhance numerical efficiency. It enables us to decrease the number of mesh points while maintaining the same mesh spacing in the momentum coordinate. The proposed scheme thus not only requires less memory but can significantly reduce the computation time. To minimize resultant loss of numerical accuracy, we also propose the partial local potential averaging method.

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Section: Introductionmentioning

confidence: 99%

An efficient numerical scheme for the discrete Wigner transport equation via the momentum domain narrowing

Kim

2016

AIP Advances

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“…Substantial work on the impact of random discrete dopants on the performance of MOSFET transistors has been carried out [6][7][8][9][10]. This work has made use of Drift-diffusion, Monte Carlo and the Non-Equilibrium Green function (NEGF) carrier transport models.…”

Section: Introductionmentioning

confidence: 99%

“…A substantial amount of theoretical work has been done in studying the performance of trigate FETs and nanowires. This work ranges from semi-classical transport studies [4] to full-band quantum transport analysis [5].Substantial work on the impact of random discrete dopants on the performance of MOSFET transistors has been carried out [6][7][8][9][10]. This work has made use of Drift-diffusion, Monte Carlo and the Non-Equilibrium Green function (NEGF) carrier transport models.…”

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NEGF simulations of a junctionless Si gate-all-around nanowire transistor with discrete dopants

Martı́nez

Aldegunde

Brown

et al. 2012

Solid-State Electronics

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We have carried out 3D Non-Equilibrium Green Function simulations of a junctionless gate-all-around ntype silicon nanowire transistor of 4.2×4.2 nm 2 crosssection. We model the dopants in a fully atomistic way. The dopant distributions are randomly generated following an average doping concentration of 10 20 cm -3 . Elastic and inelastic Phonon scattering is considered in our simulation. Considering the dopants in a discrete way is the first step in the simulation of random dopant variability in junctionless transistors in a fully quantum mechanical way. Our results show that, for devices with an "unlucky" dopant configuration, with a starvation of donors under the gate, the threshold voltage can increase by a few hundred mV relative to devices with a more homogeneous distribution of dopants. IntroductionJunctionless Field Effect Transistors (JLFET) [1-2] have been proposed as an alternative to the standard minority-carrier channel MOSFETs at the end of the road map. As transistor dimensions scale down to tens of nanometres it became increasingly complicated to control the dopants at the source/channel and channel/drain boundaries. Another related problem is the intrinsic discreteness of dopants, which makes these boundaries less well defined at the nanoscale. As the JLFET is doped all the way through from source/channel/drain at the same doping concentration it is argued that it will not suffer of variability coming from fluctuations in the effective channel length, which becomes important at channel lengths of approximately 20 nm for conventional silicon transistors. Recently, a paper from the Tyndall Institute [3] has shown, experimentally and theoretically, the potential of the JLFET. A substantial amount of theoretical work has been done in studying the performance of trigate FETs and nanowires. This work ranges from semi-classical transport studies [4] to full-band quantum transport analysis [5].Substantial work on the impact of random discrete dopants on the performance of MOSFET transistors has been carried out [6][7][8][9][10]. This work has made use of Drift-diffusion, Monte Carlo and the Non-Equilibrium Green function (NEGF) carrier transport models.Gate-all-around (GAA) nanowire transistors have a superior electrostatic integrity compared with the standard planar MOSFET architecture. When the nanowire cross-section becomes smaller than 10 nm, quantum confinement becomes important and a proper description of the sub-bands is necessary in order to properly describe quantum capacitances and the quasi-1D density of states. Furthermore, at channel lengths of less than 20 nm the tunnelling component of the sourcedrain current cannot be neglected [11]. Semi-classical simulation based on a Boltzmann description of the transport cannot capture the source-drain tunnelling.In this work we use the NEGF formalism to carry out simulations of the transfer characteristics of a junctionless Si GAA nanowire transistor. We consider the impact of the random discrete dopants in the active region of the device. Th...

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“…For a doping concentration of 10 20 cm -3 , there are only 2 dopants on average in the volume of 4 x 2.2 x 2.2 nm 3 . All simulations were carried out at drain voltage (V D ) equal to 0.05 V in order to investigate the charge density around the impurities more easily and to provide consistent comparison with previously published results [35], [36], [37]. …”

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Impact of Precisely Positioned Dopants on the Performance of an Ultimate Silicon Nanowire Transistor: A Full Three-Dimensional NEGF Simulation Study

Georgiev

Towie

Asenov

2013

IEEE Trans. Electron Devices

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n Georgiev, V.P., Towie, E.A., and Asenov, A. (2013) Impact of precisely positioned dopants on the performance of an ultimate silicon nanowire transistor: a full threedimensional NEGF simulation study. IEEE Transactions on Electron Devices, 60(3), pp. 965-971.There may be differences between this version and the published version. You are advised to consult the publisher's version if you wish to cite from it.http://eprints.gla.ac.uk/82165/ Deposited on: 16 February 2016 Enlighten -Research publications by members of the University of Glasgow http://eprints.gla.ac.uk > REPLACE THIS LINE WITH YOUR PAPER IDENTIFICATION NUMBER (DOUBLE-CLICK HERE TO EDIT) < 1Abstract-In this paper, we report the first systematic study of quantum transport simulation of the impact of precisely positioned dopants on the performance of ultimately scaled gateall-around silicon nanowire transistors (SNWT) designed for digital circuit applications. Due to strong inhomogeneity of the self-consistent electrostatic potential, a full 3-D real-space NonEquilibrium Green's Function (NEGF) formalism is used. The simulations are carried out for an n-channel NWT with 2.2 x 2.2 nm 2 cross-section and 6 nm channel length, where the locations of the precisely arranged dopants in the source drain extensions and in the channel region have been varied. The individual dopants act as localized scatters and, hence, impact of the electron transport is directly correlated to the position of the single dopants. As a result, a large variation in the ON-current and modest variation of the subthreshold slope are observed in the I D -V G characteristics when comparing devices with microscopically different discrete dopant configuration. The variations of the current-voltage characteristics are analyzed with reference to the behaviour of the transmission coefficients.Index Terms-single-atom transistor, discrete dopants, nanowire transistor, non-equilibrium Green's function (NEGF), 3-D simulations, quantum transport. I. INTRODUCTIONILICON TECHNOLOGY can deliver sub-10 nm devices where 'every atom counts'. Manipulation of atoms with high precision on such a scale, in principle, can lead to technological innovations, such as transistors with extremely short gate length [1], quantum computing components [2] and optoelectronic devices [3]. One possible strategy to create this next generation of devices is to precisely place individual discrete dopants (such as phosphorous atoms) in a nanoscale transistor [4]. The number and the spatial distribution of individual dopants within the transistor of modern silicon chips determine both their characteristics and their unwanted variability [5], [6]. Hence, it is crucial to establish a direct link between the position of individual dopants and the transistors' performance [7], [8]. At the physical limit of transistor scaling a single phosphorous atom embedded within epitaxial silicon environment, in principle, can be used to build a single-atom transistor [9]. Although such an idea looks spectacularly attractive, the side ga...

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Current Variability in Si Nanowire MOSFETs Due to Random Dopants in the Source/Drain Regions: A Fully 3-D NEGF Simulation Study

Cited by 72 publications

References 25 publications

An efficient numerical scheme for the discrete Wigner transport equation via the momentum domain narrowing

An efficient numerical scheme for the discrete Wigner transport equation via the momentum domain narrowing

NEGF simulations of a junctionless Si gate-all-around nanowire transistor with discrete dopants

Impact of Precisely Positioned Dopants on the Performance of an Ultimate Silicon Nanowire Transistor: A Full Three-Dimensional NEGF Simulation Study

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