3,874 research outputs found
A few electrons per ion scenario for the B=0 metal-insulator transition in two dimensions
We argue on the basis of experimental numbers that the B=0 metal-insulator
transition in two dimensions, observed in Si-MOSFETs and in other
two-dimensional systems, is likely to be due to a few strongly interacting
electrons, which also interact strongly with the random positively ionized
impurities. At the insulating side the electrons are all bound in pairs to the
ions. On the metallic side free electrons exist which are scattered by ions
dressed with electron-pairs and therefore alter the bare scattering potential
of the ions. The physics at the metallic side of the transition is argued to be
controlled by the classical to quantum transport cross-over leading to the
observed non-monotonous dependence of the resistivity on temperature. This few
electrons per ion scenario appears to be an experimentally realistic and
testable scenario, which can also serve as a starting point for further
theoretical analysis of the two-dimensional metal-insulator transition.Comment: 8 pages, revised version, minor change
A Backscattering Model Incorporating the Effective Carrier Temperature in Nano MOSFET
In this work we propose a channel backscattering model in which increased
carrier temperature at the top of the potential energy barrier in the channel
is taken into account. This model represents an extension of a previous model
by the same authors which highlighted the importance of considering the
partially ballistic transport between the source contact and the top of the
potential energy barrier in the channel. The increase of carrier temperature is
precisely due to energy dissipation between the source contact and the top of
the barrier caused by the high saturation current. To support our discussion,
accurate 2D full band Monte Carlo device simulations with quantum correction
have been performed in double gate nMOSFETs for different geometries (gate
length down to 10 nm), biases and lattice temperatures. Including the effective
carrier temperature is especially important to properly treat the high
inversion regime, where previous backscattering models usually fail
Absence of Localization in Certain Field Effect Transistors
We review some experimental and theoretical results on the metal-to-insulator
transition (MIT) observed at zero magnetic field (B=0) in several
two-dimensional electron systems (2DES). Scaling of the conductance and
magnetic field dependence of the conductance provide convincing evidence that
the MIT is driven by Coulomb interactions among the carriers and is
dramatically sensitive to spin polarization of the carriers.Comment: 8 pages, LaTeX, figure label change
Monte Carlo simulations of high-performance implant free In<sub>0.3</sub>Ga<sub>0.7</sub> nano-MOSFETs for low-power CMOS applications
No abstract available
Performance Evaluation of Ballistic Silicon Nanowire Transistors with Atomic-basis Dispersion Relations
In this letter, we explore the bandstructure effects on the performance of
ballistic silicon nanowire transistors (SNWTs). The energy dispersion relations
for silicon nanowires are evaluated with an sp3d5s* tight binding model. Based
on the calculated dispersion relations, the ballistic currents for both n-type
and p-type SNWTs are evaluated by using a semi-numerical ballistic model. For
large diameter nanowires, we find that the ballistic p-SNWT delivers half the
ON-current of a ballistic n-SNWT. For small diameters, however, the ON-current
of the p-type SNWT approaches that of its n-type counterpart. Finally, the
carrier injection velocity for SNWTs is compared with those for planar
metal-oxide-semiconductor field-effect transistors, clearly demonstrating the
impact of quantum confinement on the performance limits of SNWTs.Comment: 12 pages, 4 figure
Similarities and Differences in 2D `metallicity' induced by temperature and parallel magnetic field: To screen or not to screen
We compare the effects of temperature and parallel magnetic field on the
two-dimensional metallic behavior within the unified model of temperature and
field dependent effective disorder arising from the screened charged impurity
scattering. We find, consistent with experimental observations, that the
temperature and field dependence of resistivity should be qualitatively similar
in n-Si MOSFET and very different in n-GaAs 2D metallic systems.Comment: 7 pages, 5 figures, revised version with substantial additio
Breakdown of universal mobility curves in sub-100-nm MOSFETs
We explore the breakdown of universal mobility behavior in sub-100-nm Si MOSFETs, using a novel three-dimensional (3-D) statistical simulation approach. In this approach, carrier trajectories in the bulk are treated via 3-D Brownian dynamics, while the carrier-interface roughness scattering is treated using a novel empirical model
Simulation of intrinsic parameter fluctuations in decananometer and nanometer-scale MOSFETs
Intrinsic parameter fluctuations introduced by discreteness of charge and matter will play an increasingly important role when semiconductor devices are scaled to decananometer and nanometer dimensions in next-generation integrated circuits and systems. In this paper, we review the analytical and the numerical simulation techniques used to study and predict such intrinsic parameters fluctuations. We consider random discrete dopants, trapped charges, atomic-scale interface roughness, and line edge roughness as sources of intrinsic parameter fluctuations. The presented theoretical approach based on Green's functions is restricted to the case of random discrete charges. The numerical simulation approaches based on the drift diffusion approximation with density gradient quantum corrections covers all of the listed sources of fluctuations. The results show that the intrinsic fluctuations in conventional MOSFETs, and later in double gate architectures, will reach levels that will affect the yield and the functionality of the next generation analog and digital circuits unless appropriate changes to the design are made. The future challenges that have to be addressed in order to improve the accuracy and the predictive power of the intrinsic fluctuation simulations are also discussed
Scaling and the Metal-Insulator Transition in Si/SiGe Quantum Wells
The existence of a metal-insulator transition at zero magnetic field in two-
dimensional electron systems has recently been confirmed in high mobility
Si-MOSFETs. In this work, the temperature dependence of the resistivity of
gated Si/SiGe/Si quantum well structures has revealed a similar metal-
insulator transition as a function of carrier density at zero magnetic field.
We also report evidence for a Coulomb gap in the temperature dependence of
the resistivity of the dilute 2D hole gas confined in a SiGe quantum well.
In addition, the resistivity in the insulating phase scales with a single
parameter, and is sample independent. These results are consistent with the
occurrence of a metal-insulator transition at zero magnetic field in SiGe
square quantum wells driven by strong hole-hole interactions.Comment: 3 pages, 3 figures, LaTe
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