815 research outputs found
Towards Multi-Scale Modeling of Carbon Nanotube Transistors
Multiscale simulation approaches are needed in order to address scientific
and technological questions in the rapidly developing field of carbon nanotube
electronics. In this paper, we describe an effort underway to develop a
comprehensive capability for multiscale simulation of carbon nanotube
electronics. We focus in this paper on one element of that hierarchy, the
simulation of ballistic CNTFETs by self-consistently solving the Poisson and
Schrodinger equations using the non-equilibrium Greens function (NEGF)
formalism. The NEGF transport equation is solved at two levels: i) a
semi-empirical atomistic level using the pz orbitals of carbon atoms as the
basis, and ii) an atomistic mode space approach, which only treats a few
subbands in the tube-circumferential direction while retaining an atomistic
grid along the carrier transport direction. Simulation examples show that these
approaches describe quantum transport effects in nanotube transistors. The
paper concludes with a brief discussion of how these semi-empirical device
level simulations can be connected to ab initio, continuum, and circuit level
simulations in the multi-scale hierarchy
Effects of Parasitics and Interface Traps On Ballistic Nanowire FET In The Ultimate Quantum Capacitance Limit
In this paper, we focus on the performance of a nanowire Field Effect
Transistor (FET) in the Ultimate Quantum Capacitance Limit (UQCL) (where only
one subband is occupied) in the presence of interface traps (),
parasitic capacitance () and source/drain series resistance ()
using a ballistic transport model and compare the performance with its
Classical Capacitance Limit (CCL) counterpart. We discuss four different
aspects relevant to the present scenario, namely, (i) gate voltage dependent
capacitance, (ii) saturation of the drain current, (iii) the subthreshold slope
and (iv) the scaling performance. To gain physical insights into these effects,
we also develop a set of semi-analytical equations. The key observations are:
(1) A strongly energy-quantized nanowire shows non-monotonic multiple peak C-V
characteristics due to discrete contributions from individual subbands; (2) The
ballistic drain current saturates better in the UQCL compared to CCL, both in
presence and absence of and ; (3) The subthreshold slope does
not suffer any relative degradation in the UQCL compared to CCL, even with
and ; (4) UQCL scaling outperforms CCL in the ideal
condition; (5) UQCL scaling is more immune to , but presence of
and significantly degrades scaling advantages in the UQCL.Comment: Accepted at IEEE Transactions on Electron Device
Graphene Field Effect Transistors: Diffusion-Drift Theory
Based on explicit solution of current continuity equation in the graphene
FET's channel the semi-classical diffusion-drift description of the carrier
transport and I-V characteristics model has been developed. Role of
rechargeable defects (interface traps) near or at the interface between
graphene and insulated layers has also described.Comment: 24 pages, 13 figures, a chapter in "Graphene, Theory, Research and
Applications", INTEC
Transient Analysis of Warm Electron Injection Programming of Double Gate SONOS Memories by means of Full Band Monte Carlo Simulation
In this paper we investigate "Warm Electron Injection" as a mechanism for NOR
programming of double-gate SONOS memories through 2D full band Monte Carlo
simulations. Warm electron injection is characterized by an applied VDS smaller
than 3.15 V, so that electrons cannot easily accumulate a kinetic energy larger
than the height of the Si/SiO2 barrier. We perform a time-dependent simulation
of the program operation where the local gate current density is computed with
a continuum-based method and is adiabatically separated from the 2D full Monte
Carlo simulation used for obtaining the electron distribution in the phase
space. In this way we are able to compute the time evolution of the charge
stored in the nitride and of the threshold voltages corresponding to forward
and reverse bias. We show that warm electron injection is a viable option for
NOR programming in order to reduce power supply, preserve reliability and CMOS
logic level compatibility. In addition, it provides a well localized charge,
offering interesting perspectives for multi-level and dual bit operation, even
in devices with negligible short channel effects
3-D Quantum Numerical Simulation of Transient Response in Multiple-Gate Nanowire MOSFETs Submitted to Heavy Ion Irradiation
International audienc
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