Role of scattering in nanotransistors

Svizhenko, A.; Anantram, M. P.

doi:10.1109/ted.2003.813503

Cited by 196 publications

(101 citation statements)

References 27 publications

(33 reference statements)

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“…We now discuss how much the real part of electron-phonon retarded selfenergy ℜe[Σ R ph,q (E)] and thus the renormalization of the density of states affects the potential profile. In previous studies [21] ℜe[Σ R ph,q (E)] was set to zero, which naturally alleviates computational requirements. In Fig.2 we show the density of states of crossing subbands versus energy in a (12, 0) nanotube under a zero bias.…”

Section: Formalismmentioning

confidence: 99%

Effect of scattering and contacts on current and electrostatics in carbon nanotubes

2005

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We computationally study the electrostatic potential profile and current carrying capacity of carbon nanotubes as a function of length and diameter. Our study is based on solving the non equilibrium Green's function and Poisson equations self-consistently, including the effect of electronphonon scattering. A transition from ballistic to diffusive regime of electron transport with increase of applied bias is manifested by qualitative changes in potential profiles, differential conductance and electric field in a nanotube. In the low bias ballistic limit, most of the applied voltage drop occurs near the contacts. In addition, the electric field at the tube center increases proportionally with diameter. In contrast, at high biases, most of the applied voltage drops across the nanotube, and the electric field at the tube center decreases with increase in diameter. We find that the differential conductance can increase or decrease with bias as a result of an interplay of nanotube length, diameter and a quality factor of the contacts. From an application view point, we find that the current carrying capacity of nanotubes increases with increase in diameter. Finally, we investigate the role of inner tubes in affecting the current carried by the outermost tube of a multiwalled nanotube.

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Section: Formalismmentioning

confidence: 99%

Effect of scattering and contacts on current and electrostatics in carbon nanotubes

2005

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“…Memory dressing describes the cumulative effect of the S − E interaction, as witnessed by a quadratic feedback term in its self-contained matrix Riccati 54,55 equation of motion (below). The other new quantity occurring in (8), V(t, 0), can be perceived as the evolution operator for the states from subspace 2, and is important for the description of the influx of information from E to S. R and V obey…”

Section: B Equations With Memory Dressingmentioning

confidence: 99%

“…In the absence of scattering within the active region, the coupling of the active region to the contacts is the cause of its nonunitary evolution (decoherence) towards a nonequilibrium steady state, and the importance of this coupling has become wellrecognized in quantum transport studies. The description and manipulation of the contact-induced decoherence are presently of great importance not only in quantum transport studies, 4,5,6,7,8,9,10,11,12 but also in the theory of measurement 13 and quantum information. 14 The purpose of this paper is to provide a simple description of the nonunitary evolution of a ballistic nanostructure's active region due to the injection of carriers from the contacts.…”

Section: Introductionmentioning

confidence: 99%

Decoherence due to contacts in ballistic nanostructures

Knežević

2008

Phys. Rev. B

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The active region of a ballistic nanostructure is an open quantum-mechanical system, whose nonunitary evolution (decoherence) towards a nonequilibrium steady state is determined by carrier injection from the contacts. The purpose of this paper is to provide a simple theoretical description of the contact-induced decoherence in ballistic nanostructures, which is established within the framework of the open systems theory. The active region's evolution in the presence of contacts is generally non-Markovian. However, if the contacts' energy relaxation due to electron-electron scattering is sufficiently fast, then the contacts can be considered memoryless on timescales coarsened over their energy relaxation time, and the evolution of the current-limiting active region can be considered Markovian. Therefore, we first derive a general Markovian map in the presence of a memoryless environment, by coarse-graining the exact short-time non-Markovian dynamics of an abstract open system over the environment memory-loss time, and we give the requirements for the validity of this map. We then introduce a model contact-active region interaction that describes carrier injection from the contacts for a generic two-terminal ballistic nanostructure. Starting from this model interaction and using the Markovian dynamics derived by coarse-graining over the effective memory-loss time of the contacts, we derive the formulas for the nonequilibrium steady-state distribution functions of the forward and backward propagating states in the nanostructure's active region. On the example of a double-barrier tunneling structure, the present approach yields an I-V curve that shows all the prominent resonant features. We address the relationship between the present approach and the Landauer-Büttiker formalism, and also briefly discuss the inclusion of scattering.

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“…Lake also begun development of a full band 3-D NEGF model [38,39]. Anantram, Datta, Lundstrom, Jovanovic, and Ogawa have pushed forward NEGF device simulation for ultra-scaled CMOS devices where a 2-D spatial domain is resolved [40,41,6,42]. NEGF usage is also expanding into the novel field of molecular electronics [43,5] and even software has emerged on the commercial market [44].…”

Section: Negf and Other Simulatorsmentioning

confidence: 99%

NEMO 1-D: the first NEGF-based TCAD tool

Klimeck

2004

Simulation of Semiconductor Processes and Devices 2004

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The fundamentally sound non-Equilibrium Green's function (NEGF) approach provides the theoretical basis for NEMO 1-D as the first nanoelectronic TCAD tool. Effects of quantum charging, bandstructure and incoherent scattering from alloy disorder, interface roughness, acoustic phonons, and polar optical phonons are modeled. Engineers and experimentalists who desire a black-box design tool as well as theorists who are interested in a detailed investigation of the physics have found NEMO useful. Access to this comprehensive theoretical framework is accommodated by a graphical user interface (GUI) which configures the usage of a collection of models that trade off physical content with speed and memory requirements. This article describes the NEMO origin, provides modern references to NEGF, accumulates the diverse references to the NEMO results, and provides a perspective on NEGF in future TCAD tools. History and AcknowledgementsThe nanoelectronic modeling (NEMO) program is the result of a multi-year development effort involving an industrial research laboratory (Central Research Laboratory of Texas Instruments, later transferred to Raytheon TI Systems), several Universities (UT Dallas, Ohio State U., U. Alabama in Huntsville), and a US Federally Funded Development and Research Center (NASA, JPL, California Institute of Technology). The original development began in 1993 with the lead of TI and concluded with the delivery of the tool to the US government sponsor in January of 1998. The development then shifted to the NASA Jet Propulsion Laboratory. A large number of people involved with the NEMO 1-D code over the past 11 years. I would especially like to acknowledge the key contributors to the development of the tool: Drs. Roger Lake, R. Chris Bowen, Dan Blanks, Bill Frensley, and Tim Boykin. The primary application focus was the quantitative modeling of resonant tunneling diodes (RTDs). These III-V high speed devices were developed for high speed applications such as analog-digital-converters [1] and memory devices [2]. Modern NEGF Method References for Carrier TransportNovel aspects of the theory developed under the NEMO program are described in detail in [3]. Early work on the NEGF approach has been focussed on bulk many-body interactions and the literature was difficult to penetrate. Just over the past few years Datta has published [4,5] introductions to NEGF that enable the electrical engineer to

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Role of scattering in nanotransistors

Cited by 196 publications

References 27 publications

Effect of scattering and contacts on current and electrostatics in carbon nanotubes

Effect of scattering and contacts on current and electrostatics in carbon nanotubes

Decoherence due to contacts in ballistic nanostructures

NEMO 1-D: the first NEGF-based TCAD tool

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