A Self-Consistent Full 3-D Real-Space NEGF Simulator for Studying Nonperturbative Effects in Nano-MOSFETs

Martı́nez, Antonio; Bescond, Marc; Barker, John R.; Svizhenko, A.; Anantram, M. P.; Millar, C.; Asenov, A.

doi:10.1109/ted.2007.902867

Cited by 139 publications

(81 citation statements)

References 20 publications

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“…An inhouse NEGF simulator [14] based in an efficient coupled-mode approach using a recursive algorithm is used. This simulator has been recently benchmarked [14] with our full 3D real-space NEGF simulator [15]. The Hamiltonian is written in the effective mass approximation.…”

Section: Device and Transport Modelmentioning

confidence: 99%

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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Section: Device and Transport Modelmentioning

confidence: 99%

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

Martı́nez

Aldegunde

Brown

et al. 2012

Solid-State Electronics

Self Cite

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“…7 In order to be able to solve the problem in a computation-efficient manner we adopt the mode-space approach. The ID Schrödinger in the transport direction for each mode can be written as: 4,12,19 …”

Section: ͑2͒mentioning

confidence: 99%

“…Different groups have modeled the electrical characteristics of multigate silicon nanowires in the ballistic transport regime using techniques based on the Schrödinger equation, the Wigner function, the density matrix or the nonequilibrium Green's function ͑NEGF͒ method. [4][5][6][7][8] The NEGF approach has been successfully used to model different types of low-dimensional structures such as carbon nanotube FETs, quantum-well devices, silicon nanowire transistors, and molecular devices. 7,[9][10][11] The reason for the wide acceptance of the NEGF method lies in the ability it has to handle different types of elastic and inelastic scattering mechanisms such as electron-phonon and surface roughness.…”

Section: Introductionmentioning

confidence: 99%

“…[4][5][6][7][8] The NEGF approach has been successfully used to model different types of low-dimensional structures such as carbon nanotube FETs, quantum-well devices, silicon nanowire transistors, and molecular devices. 7,[9][10][11] The reason for the wide acceptance of the NEGF method lies in the ability it has to handle different types of elastic and inelastic scattering mechanisms such as electron-phonon and surface roughness. Different groups have investigated the effect of dissipative scattering on the electronic transport and electrical characteristics in structures such as CNTFETs and quantum-well devices.…”

Section: Introductionmentioning

confidence: 99%

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Effect of intravalley acoustic phonon scattering on quantum transport in multigate silicon nanowire metal-oxide-semiconductor field-effect transistors

Akhavan

Afzalian

Lee

et al. 2010

Journal of Applied Physics

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In this paper we investigate the effects of intravalley acoustic phonon scattering on the quantum transport and on the electrical characteristics of multigate silicon nanowire metal-oxide-semiconductor field-effect transistors. We show that acoustic phonons cause a shift and broadening of the local DOS in the nanowire, which modifies the electrical characteristics of the device. The influence of scattering on off-state and on-state currents is investigated for different values of channel length. In the ballistic transport regime, source-to-drain tunneling current is predominant, whereas in the presence of acoustic phonons, diffusion becomes the dominant current transport mechanism. A three-dimensional quantum mechanical device simulator based on the nonequilibrium Green's function formalism in uncoupled-mode space has been developed to extract device parameters in the presence of electron-phonon interactions. Electron-phonon scattering is accounted for by adopting the self-consistent Born approximation and using the deformation potential theory.

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“…We opted for the nearest- one momentum-energy combination, 14 hours is the lowest limit to treat one bias point, without even considering the self-consistency of the electrostatic potential and carrier density. Until recently it was not clear whether a multidimensional and quantum-mechanical simulation of nanodevices was possible without neglecting some important characteristics like the full bandstructure (effective mass approximation) or the unity of the simulation domain (mode space approximation) [7], [8].…”

Section: Introductionmentioning

confidence: 99%

A multi-level parallel simulation approach to electron transport in nano-scale transistors

Luisier¹,

Klimeck²

2008

2008 SC - International Conference for High Performance Computing, Networking, Storage and Analysis

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Physics-based simulation of electron transport in nanoelectronic devices requires the solution of thousands of highly complex equations to obtain the output characteristics of one single input voltage. The only way to obtain a complete set of bias points within a reasonable amount of time is the recourse to supercomputers offering several hundreds to thousands of cores. To profit from the rapidly increasing availability of such machines we have developed a state-of-the-art quantum mechanical transport simulator dedicated to nanodevices and working with four levels of parallelism. Using these four levels we demonstrate that an almost ideal scaling of the walltime up to 32768 processors with a parallel efficiency of 86% is reached in the simulation of realistically extended and gated field-effect transistors.Obtaining the current characteristics of these devices is reduced to some hundreds of seconds instead of days on a small cluster or months on a single CPU.

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A Self-Consistent Full 3-D Real-Space NEGF Simulator for Studying Nonperturbative Effects in Nano-MOSFETs

Cited by 139 publications

References 20 publications

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

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

Effect of intravalley acoustic phonon scattering on quantum transport in multigate silicon nanowire metal-oxide-semiconductor field-effect transistors

A multi-level parallel simulation approach to electron transport in nano-scale transistors

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