2,011 research outputs found
Engineering interband tunneling in nanowires with diamond cubic or zincblende crystalline structure based on atomistic modeling
We present an investigation in the device parameter space of band-to-band
tunneling in nanowires with a diamond cubic or zincblende crystalline
structure. Results are obtained from quantum transport simulations based on
Non-Equilibrium Green's functions with a tight-binding atomistic Hamiltonian.
Interband tunneling is extremely sensitive to the longitudinal electric field,
to the nanowire cross section, through the gap, and to the material. We have
derived an approximate analytical expression for the transmission probability
based on WKB theory and on a proper choice of the effective interband tunneling
mass, which shows good agreement with results from atomistic quantum
simulation.Comment: 4 pages, 3 figures. Final version, published in IEEE Trans.
Nanotechnol. It differs from the previous arXiv version for the title and for
some changes in the text and in the reference
Carrier Transport in High Mobility InAs Nanowire Junctionless Transistors
Ability to understand and model the performance limits of nanowire
transistors is the key to design of next generation devices. Here, we report
studies on high-mobility junction-less gate-all-around nanowire field effect
transistor with carrier mobility reaching 2000 cm2/V.s at room temperature.
Temperature-dependent transport measurements reveal activated transport at low
temperatures due to surface donors, while at room temperature the transport
shows a diffusive behavior. From the conductivity data, the extracted value of
sound velocity in InAs nanowires is found to be an order less than the bulk.
This low sound velocity is attributed to the extended crystal defects that
ubiquitously appear in these nanowires. Analyzing the temperature-dependent
mobility data, we identify the key scattering mechanisms limiting the carrier
transport in these nanowires. Finally, using these scattering models, we
perform drift-diffusion based transport simulations of a nanowire field-effect
transistor and compare the device performances with experimental measurements.
Our device modeling provides insight into performance limits of InAs nanowire
transistors and can be used as a predictive methodology for nanowire-based
integrated circuits.Comment: 22 pages, 5 Figures, Nano Letter
Analytical model of nanowire FETs in a partially ballistic or dissipative transport regime
The intermediate transport regime in nanoscale transistors between the fully
ballistic case and the quasi equilibrium case described by the drift-diffusion
model is still an open modeling issue. Analytical approaches to the problem
have been proposed, based on the introduction of a backscattering coefficient,
or numerical approaches consisting in the MonteCarlo solution of the Boltzmann
transport equation or in the introduction of dissipation in quantum transport
descriptions. In this paper we propose a very simple analytical model to
seamlessly cover the whole range of transport regimes in generic quasi-one
dimensional field-effect transistors, and apply it to silicon nanowire
transistors. The model is based on describing a generic transistor as a chain
of ballistic nanowire transistors in series, or as the series of a ballistic
transistor and a drift-diffusion transistor operating in the triode region. As
an additional result, we find a relation between the mobility and the mean free
path, that has deep consequences on the understanding of transport in nanoscale
devices
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
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