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

We have studied the carrier profile and calculated a unique effective mass for a two-dimensional
hole gas confined in a SiO2/Si/Si1_xGex/Si structure when an external
voltage is applied. For this purpose, we have solved the system of differential equations
provided by the 6 x 6 Luttinger Hamiltonian [1] simultaneously with the Poisson
equation, applying an iterative process until convergence was achieved. This enabled us
to incorporate the warping and the strong coupling among the subbands that constitute
the band structure [2].From the calculated density of carriers we were able to evaluate an average effective
mass. Although our calculations indicate that this effective mass varies notably with the
hole confinement level, in general, we observed a decrease in the calculated effective
mass as the molar fraction of Ge increases, which might justify the use of this kind of
device.

Salvador Rodríguez

J. Banqueri

J. E. Carceller

Evaluation of an Equivalent Hole Effective Mass
for Si/SiGe Structures

Silicon-hydrogen bonds passivate the interface defects at the silicon-silicon dioxide
interface of CMOS transistors. The activation of these bonds and subsequent creation
of interface traps is an important source of transistor degradation at current operating
conditions. There is now evidence for a distribution in the activation energies of these
bonds instead of a single threshold value. We show that conventional CMOS scaling
rules are substantially affected by this energy distribution, as it causes an increased
probability of smaller devices having lower activation thresholds and therefore faster
activation times. Further, we quantify the voltage shift necessary to overcome the
decreased yield due to the increased number of early device failures, and show, for
0.1 μm MOSFET scaling, that this shift can be a considerable fraction of the
conventionally designed supply voltage.

Amr Haggag

William McMahon

Karl Hess

Björn Fischer

Leonard F. Register

Impact of Scaling on CMOS Chip Failure Rate,
and Design Rules for Hot Carrier Reliability

With the progress of integrated technology, the feature size of experimental electron
devices have already been scaled down deeply into the sub–0.1 μm region. For such
ultra-small devices, it is increasingly important to take quantum mechanical effects into
account for device simulation. In this paper, we present a new approach for quantum
modeling, applicable to multi-dimensional ultra-small device simulation. In this work,
the quantum effects are represented in terms of quantum mechanically corrected
potential in the classical Boltzmann equation. We apply the Monte Carlo method to
solve the quantum transport equation, and demonstrate that the quantum effects such
as tunneling and quantum confinement effects can be incorporated in the standard
Monte Carlo techniques.

Hideaki Tsuchiya

Brian Winstead

Umberto Ravaioli

Quantum Potential Approaches
for Nano-scale Device Simulation

We present an investigation of the process of charging and discharging of the floatinggate of thin oxide Flash EEPROMs based on a fully quantum mechanical approach totransport in the vertical direction. Our approach allows us to compute program, erase,and retention times as a function of the gate stack structure, and applied voltages.

G.  Iannaccone

S.  Gennai

Program, Erase and Retention Timesof Thin-oxide Flash-EEPROMs

A 2D-Hydrodynamic model is carried out to predict the breakdown voltage ofmicrowave field effect transistors. The model is based on the conservation equationsinferred from Boltzmann&#39;s transport equation, coupled with Poisson’s equation. Inorder to take into account the channel avalanche breakdown, the charge conservationequations for electrons and holes are considered and a generation term is introduced.The set of equations is solved using finite difference and different computationalmethods have been tested to save computing time. The model allows us to obtainaccurate predictions for power transistors considering a usual gate recess. Results areperformed for pseudomorphic ALGaAs/InGaAs/GaAs HEMTs.

M.  Rousseau

J. C. De Jaeger

2D-Hydrodynamic Energy Model IncludingAvalanche Breakdown Phenomenon for PowerField Effect Transistors

The strain-dependence of electron transport in bulk Si and deep-submicron MOSFETsis investigated by full-band Monte Carlo simulation. On the bulk level, the drift velocityat medium field strengths is still enhanced above Ge-contents of 20&#37; in the substrate,where the low-field mobility is already saturated, while the saturation velocity remainsunchanged under strain. In an n-MOSFET with a metallurgical channel length of50nm, the saturation drain current is enhanced by up to 11&#37;, but this maximumimprovement is essentially already achieved at a Ge-content of 20&#37; emphasizing therole of the low-field mobility as a key indicator of device performance in the deep-submicronregime.

F. M. Bufler

P. D. Yoder

W.  Fichtner

Strain-Dependence of Electron Transport in BulkSi and Deep-Submicron MOSFETs

John R. Barker

Asen  Asenov

IWCE-7 Committees

The behavior of short-wave-length acoustic phonons in the vicinity of a quantum well in
a GaAs/AlGaAs heterostructure has been investigated. Hot two-dimensional electrons
in the well produce longitudinal optical phonons, which decay into almost monoenergetic
short-wave-length longitudinal acoustic (LA) phonons. The latter undergo
elastic scattering and down-conversion into transverse acoustic (TA) phonons. The distribution
of the LA and TA phonons over frequency and distance to the well have
been found by solving semi-analytically a system of two kinetic equations with nontrivial
boundary conditions and nonlinear dispersion. The distribution functions have
essentially non-temperature form even at substantial distance from the well.

D. A. Romanov

J. Eizenkop

V. V. Mitin

Dynamics of Non-equilibrium Short-wave-length
Phonons in Semiconductor Heterostructures

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