John  Barker

Guest Editorial

A careful calibration of a continuum process simulator is normally required to achieve agood agreement between simulated results and experimental dopant profiles. However,the validity of such a calibration procedure is often limited to a particular technology.By taking into account a number of physics-based models and experimental resultsavailable in literature, the predicting capability of the process simulation has beenconveniently improved. In particular, this paper shows how concentration-depthprofiles from two different CMOS technologies have been successfully reproduced witha unique set of fitting parameters.

M.  Lorenzini

L.  Haspeslagh

J.  Van Houdt

H. E. Maes

Simulation of 0.35 &#956;m/0.25 &#956;m CMOSTechnology Doping Profiles

We have introduced in a simple and efficient manner quantum mechanical corrections in
our 3D ’atomistic’ MOSFET simulator using the density gradient formalism. We have
studied in comparison with classical simulations the effect of the quantum mechanical
corrections on the simulation of random dopant induced threshold voltage fluctuations,
the effect of the single charge trapping on interface states and the effect of the oxide
thickness fluctuations in decanano MOSFETs with ultrathin gate oxides. The introduction
of quantum corrections enhances the threshold voltage fluctuations but does not
affect significantly the amplitude of the random telegraph noise associated with single
carrier trapping. The importance of the quantum corrections for proper simulation
of oxide thickness fluctuation effects has also been demonstrated.

A. Asenov

G. Slavcheva

S. Kaya

R. Balasubramaniam

Quantum Corrections to the ‘Atomistic’
MOSFET Simulations

We analyse the frequency dependent conductivity of a system which is fabricated usingthe combination of a quasi 2-dimensional MBE grown metal film and an ordered self-assembledoverlayer of adsorbed molecules. The molecules can self-assemble to formquasi 1-dimensional conducting columns, in which electrons can be temporarilytrapped. Given the short mean free path of conducting electrons, due to surface andimpurity scattering, the long range transport is modelled using a diffusion schemethrough a discrete lattice, whose sites are defined by the locations of the self-organisedmolecular columns. Local conductivities are computed using the Kubo formalism andmapped into effective transfer rates between adjacent sites of the lattice. This modelincludes stochastic excursions of electrons into the molecular states, as well as thequantum mechanical details of short range transport. External nano-engineered gatefields can be used to control the residence time of carriers in molecular bands.Calculations demonstrate that the in-plane conductivity is decreased at low frequencydue to electron capture in the molecular columns, and that this effect becomes strongeras the length of the columns is increased.

A.  Pecchia

B.  Movaghar

R. W. Kelsall

A.  Bourlange

S. D. Evans

B. J. Hickey

N.  Boden

Electronic Transport in Self-organised MolecularNanostructured Devices

We report Monte Carlo calculations of the amplification spectrum of microwave
generation in bulk GaN and its dependence on applied electric fields, doping level,
lattice temperature, etc. The amplification is shown to occur in a wide frequency range
of 0.05 to 3 THz with an optimal generation efficiency of about 1 ∼ 2%.

E. Starikov

P. Shiktorov

V. Gruinskis

L. Reggiani

L. Varani

J. C. Vaissière

Jian H. Zhao

Monte Carlo Calculations of Amplification Spectrum for GaN THz Transit-time Resonance Maser

To calculate the noise in submicron structures we need the knowledge of the local noise
sources and the generalised impedance fields. The scattered packet method has been
used to obtain both quantities at the same microscopic level. Numerical procedures used
for the calculation of velocity and energy noise sources and the simulation of the spatiotemporal
evolution of local perturbations introduced on velocity or energy are described
and some results obtained for p-type silicon are given.

P. Gaubert

J. P. Nougier

E. Starikova

V. Gruzhinskis

Scattered Packet Method for the Simulation
of the Spatio-temporal Evolution of Local Perturbations

A quantum beam of conserved particles is described as a Stationary Incoherent
Superposition of Wave packets (SISOW). Mean values of a SISOW are time-independent
confirming that the SISOW describes a stationary flux of particles. The SISOW
is a general entity that contains the Hamiltonian eigenstates as a particular limit.
The decomposition of the SISOW into wave packets provides intrinsic dynamic information
which is not accessible from Hamiltonian eigenstates. Within the SISOW
approach an exhaustive framework can be developed to be able to study dynamic
phenomena in quantum electronic devices such us current fluctuations, relaxation and
transient phenomena.

Xavier Oriols

Jordi Suñé

Study of Electronic Transport in Tunneling
Devices Using an Incoherent Superposition
of Time Dependent Wave Packets

Electron transport in model Si nanotransistors is examined by numerical simulation
using a hierarchy of simulation methods, from full Boltzmann, to hydrodynamic, energy
transport, and drift-diffusion. The on-current of a MOSFET is shown to be limited by
transport across a low-field region about one mean-free-path long and located at the beginning
of the channel. Commonly used transport models based on simplified solutions
of the Boltzmann equation are shown to fail under such conditions. The cause for
this failure is related to the neglect of the carriers' drift energy and to the collision-dominated
assumptions typically used in the development of simplified transport
models.

Kausar Banoo

Jung-Hoon Rhew

Mark Lundstrom

Chi-Wang Shu

Joseph W. Jerome

Simulating Quasi-ballistic Transport
in Si Nanotransistors

In the spirit of reviewing various approaches to the modeling and simulation of optoelectronicdevices, we discuss two specific examples, related respectively to SemiconductorOptical Amplifiers and to Quantum Cascade Lasers. In the former case, atight-binding analysis is performed aimed at the optimization of the polarizationindependence of the device. Further, a rate-equation model is set up to describe thedynamics of gain recovery after optical pumping. A Monte Carlo simulation of asuperlattice quantum cascade laser is then presented which provides an insight into themicroscopic processes controlling the performance of this device.

Paolo  Lugli

Fabio  Compagnone

Aldo Di Carlo

Andrea  Reale

Simulation of Optoelectronic Devices

We present a numerical simulation of the operation of a chain of 3 Quantum Cellular
Automanton (QCA) cells, with the inclusion of a realistic procedure to enforce, with an
externally applied bias voltage unbalance, the polarization of the first cell. The
polarization state is shown to propagate correctly, as long as the bias unbalance applied
to the electrodes of the first cell is not so large as to directly perturb nearby cells. The
addition of dummy cells is needed to balance the asymmetries existing at the ends of a
chain: this is an indication of further difficulties, that may become relevant if fabrication
of more complex arrays is attempted.

M. Girlanda

M. Macucci

Simulation of a Complete Chain of QCA Cells
with Realistic Potentials

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