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Rapid NEGF-based calculation of ballistic current in ultra-short DG MOSFETs for circuit simulation

Hosenfeld F., Horst F.., Graef M., Farokhnejad A., Kloes A., Iniguez B., Lime F.

International Journal of Microelectronics and Computer Science

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2016

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Vol. 7, nr 2

65--72

EN

Shrinking gate length in conventional MOSFETs leads to increasing short channel effects like source-to-drain (SD) tunneling. Compact modeling designers are challenged to model these quantum mechanical effects. The complexity lies in the set-up between time efficiency, physical model relation and analytical equations. Multi-scale simulation bridges the gap between compact models, its fast and efficient calculation of the device terminal voltages, and numerical device models which consider the effects of nanoscale devices. These numerical models iterate between Poisson- and Schroedinger equation which significantly slows down the simulation performance. The physicsbased consideration of quantum effects like the SD tunneling makes the non-equilibrium Green’s function (NEGF) to a stateof-the-art method for the simulation of devices in the sub 10 nm region. This work introduces a semi-analytical NEGF model for ultra-short DG MOSFETs. Applying the closed-form potential solution of a classical compact model, the model turns the NEGF from an iterative numerical solution into a straightforward calculation. The applied mathematical approximations speed up the calculation time of the 1D NEGF. The model results for the ballistic channel current in DG-MOSFETs are compared with numerical NanoMOS TCAD [1] simulation data. Shown is the accurate potential calculation as well as the good agreement of the current characteristic for temperatures down to 75 K for channel lengths from 6 nm to 20 nm and channel thickness from 1.5 nm to 3 nm.

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Conductance quantization in magnetic and nonmagnetic metallic nanowires

Susła B., Wawrzyniak M., Barnaś J., Nawrocki W.

Materials Science Poland

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2007

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Vol. 25, No. 2

303--312

EN

Transport properties of ferromagnetic quantum wires at room temperature are not yet fully understood, and the role of electronic structure of magnetic atoms in the conductance quantization is still under discussion. We present experimental results on the conductance quantization in point contacts between ferromagnetic (Co) or nonmagnetic (Au) wires and semiconductor (Ge) samples. The main features of the conductance histograms for the nonmagnetic wires are consistent with the conductance quantization in the units of quantum conductance G0 = 2e2/h. For the ferromagnetic Co nanowires, the conductance shows plateaus at nG0, generally with non-integer n. Such behaviour is a consequence of the complex electronic structure of magnetic 3d transition-metal atoms. A description of the quantization phenomena is presented in terms of the Landauer formalism for the current flowing through a small nanoconstriction.

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SOI nanodevices and materials for CMOS ULSI

Palestra F.

Journal of Telecommunications and Information Technology

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2007

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nr 2

3-13

EN

A review of recently explored new effects in SOI nanodevices and materials is given. Recent advances in the understanding of the sensitivity of electron and hole transport to the tensile or compressive uniaxial and biaxial strains in thin film SOI are presented. The performance and physical mechanisms are also addressed in multi-gate Si, SiGe and Ge MOSFETs. The impact of gate misalignment or underlap, as well as the use of the back gate for charge storage in double-gate nanodevices and of capacitorless DRAMare also outlined.