bluuebunny/crossref_metadata_2025 huggingface dataset:
On Generating Optimal Signal Probabilities for Random Tests: A Genetic Approach
Authors: Srinivas M. , Patnaik L. M.
Published: September 2007

Genetic Algorithms are robust search and optimization techniques. A Genetic Algorithm based approach for determining the optimal input distributions for generating random test vectors is proposed in the paper. A cost function based on the COP testability measure for determining the efficacy of the input distributions is discussed. A brief overview of Genetic Algorithms (GAs) and the specific details of our implementation are described. Experimental results based on ISCAS‐85 benchmark circuits are presented. The performance of our GAbased approach is compared with previous results. While the GA generates more efficient input distributions than the previous methods which are based on gradient descent search, the overheads of the GA in computing the input distributions are larger.

To account for the relatively quick convergence of the gradient descent methods, we analyze the landscape of the COP‐based cost function. We prove that the cost function is unimodal in the search space. This feature makes the cost function amenable to optimization by gradient‐descent techniques as compared to random search methods such as Genetic Algorithms.
A Multi‐Terminal Net Router for Field‐Programmable Gate Arrays
Authors: Bhatia Dinesh , Chowdhary Amit
Published: September 2007

This paper presents a router for routing multi‐terminal nets in field‐programmable gate arrays (FPGAs). The router does not require pre‐assignment of routing channels, a phase that is normally accomplished during global routing. This direct routing approach greatly enhances the probability of routing (routability). The multi‐terminal routing greatly reduces the total wire length as it approximates a Steiner tree. The total number of segments required to route the circuits is usually less as compared to other routing approaches. The router has generated excellent routing results for some industrial circuits. The memory requirements for this router are very low. The time needed for the routing is linear with respect to the size of the circuit.
Fault Modeling of ECL for High Fault Coverage of Physical Defects
Authors: Menon Sankaran M. , Malaiya Yashwant K. , Jayasumana Anura P.
Published: September 2007

Bipolar Emitter Coupled Logic (ECL) devices can now be fabricated at higher densities and consumes much lower power. Behaviour of simple and complex ECL gates are examined in the presence of physical faults. The effectiveness of the classical stuck‐at model in representing physical failures in ECL gates is examined. It is shown that the conventional stuck‐at fault model cannot represent a majority of circuit level faults. A new augmented stuck‐at fault model is presented which provides a significantly higher coverage of physical failures. The model may be applicable to other logic families that use logic gates with both true and complementary outputs. A design for testability approach is suggested for on‐line detection of certain error conditions occurring in gates with true and complementary outputs which is a normal implementation for ECL devices.
An Efficient Algorithm for the Split K‐Layer Circular Topological Via Minimization Problem
Authors: Huang J. S. , Chin Y. H.
Published: September 2007

The split k‐layer (k ≥ 2) circular topological via minimization (k‐CTVM) problem is reconsidered here. The problem is finding a topological routing of the n nets, using k available layers, such that the total number of vias is minimized. The optimal solution of this problem is solved in O(n2k+1) time. However, such an algorithm is inefficient even for n ≥ 8 and k ≥ 2. A heuristic algorithm with complexity of O(k n4) is presented. When the experimental results of this algorithm and that of an exhaustive algorithm are compared, the same number of optimal solutions is obtained from this heuristic algorithm for all permutations of 1) n = 8 with k = 2 or 3, and 2) n = 10 with k = 3. For other cases, the number of optimal solutions from this algorithm depends on the permutations been selected; and this number, in general, will increase as k increases.
DP‐FPGA: An FPGA Architecture Optimized for Datapaths
Authors: Cherepacha Don , Lewis David
Published: September 2007

This paper presents a new Field‐Programmable Gate Array (FPGA) architecture which reduces the density gap between FPGAs and Mask‐Programmed Gate Arrays (MPGAs) for datapath oriented circuits. This is primarily achieved by operating on data as a number of identically programmed four‐bit slices. The interconnection network incorporates distinct sets of resources for routing control and data signals. These features reduce circuit area by sharing programming bits among four‐bit slices, reducing the total number of storage cells required.

This paper discusses the requirements of logic blocks and routing structures that can be used to implement typical circuits containing a number of regularly structured datapaths of various sizes, as well as a small number of irregularities. It proposes a specific set of logic block architectures and analyzes it empirically. Experimental results show that the block with the smallest estimated area contains the following features: a lookup table with four read ports, a dedicated carry chain using a bidirectional four‐bit carry skip circuit, a four‐bit
register with enable and direct input capabilities, and four three‐state buffers. Further estimates of implementation area predict that the area of a design′s datapath can be reduced by a factor of approximately two compared to a conventional FPGA through the use of programming bit sharing.
Effective Coupling Between Logic Synthesis and LayoutTools for Synthesis of Area and Speed‐Efficient Circuits
Authors: Chandrasekhar Mandalagiri S. , McCharles Robert H. , Wallace David E.
Published: September 2007

Traditionally logic synthesis and layout tools optimize designs without interaction between
them. Lack of communication between the two tools often results in inferior post‐layout
circuit implementations. This paper presents three aspects of coupling synthesis with layout
to minimize post‐layout area and delay of circuits. It presents two new techniques for computing
net-weights based on timing slacks, and shows how performance improvement with
little overhead in area can be achieved. Secondly, it presents a novel idea of exploiting logic
equivalence information in circuits to minimize circuit area and delay during layout. An
algorithm for computing logic equivalence classes and performing net swapping using the
equivalence classes during layout is described. Lastly, it shows the sensitivity of post‐layout
delays of circuits to wiring models used in synthesis and demonstrates how resynthesis
techniques can be effectively used to generate good post‐layout implementation. Significant
reductions in post‐layout area and delay on several industrial designs have been observed.
VLSI Testing for High Reliability: Mixing IDDQ TestingWith Logic Testing
Authors: Hwang S. , Rajsuman R.
Published: September 2007

In this paper, we examine the effectiveness of combined logic and IDDQ
testing to detect
stuck‐at and bridging faults. The stuck‐at faults are detected by the logic test and IDDQ

testing detects bridging faults.

Near minimal stuck‐at test sets are used for this combined logic and IDQQ test environment.
These near minimal stuck‐at test sets are generated using standard test programs, while
using collapsed fault lists. We examined ISCAS ′85 and ISCAS ′89 benchmark circuits
under this combined test environment. A comparison is given for the fault coverage obtained
under this combined test environment with other studies based on pure logic test and IDDQ

test. Also, the results of IDDQ
based test sets (vectors generated specifically for IDDQ
testing)
are compared with that of stuck‐at test sets. Finally, we present a case study on a microprogrammed
processor using a functional test set to detect bridging faults in IDDQ
testing.
Monte Carlo Simulations of Impact Ionization Feedback in MOSFET Structures
Authors: Bude Jeff D.
Published: September 2007

Although impact ionization feedback is recognized as an important current multiplication
mechanism, its importance as a carrier heating mechanism has been largely
overlooked. This work emphasizes the inclusion of impact ionization feedback in Monte
Carlo device simulations, and its implications for carrier heating in sub‐micron CMOS
and EEPROM technologies.
Modeling of Radiation Fields in a Sub‐PicosecondPhoto‐Conducting System
Authors: Remley K. A. , Weisshaar A. , Tripathi V. K. , Goodnick S. M.
Published: September 2007

FDTD and Monte Carlo methods are combined to simulate the terahertz radiation
from a coplanar photoconducting structure. The simulation tool under consideration
allows calculation of potentials, particle distributions, current densities, and the near
field electromagnetic fields anywhere in the computational domain. To model the far
field radiation, it is not efficient nor, in many cases, physically possible at present to use
the FDTD technique directly because of the excessive computational burden.
Techniques are discussed for modeling both the near field and the far field radiation.
Computational results showing the far field radiation are in qualitative agreement with
published experimental results.
Smooth Quantum Hydrodynamic Model Simulationof the Resonant Tunneling Diode
Authors: Gardner Carl L. , Ringhofer Christian
Published: September 2007

Smooth quantum hydrodynamic (QHD) model simulations of the resonant tunneling
diode are presented which exhibit enhanced negative differential resistance (NDR) when
compared to simulations using the original O(ℏ2) QHD model. At both 300 K and 77 K,
the smooth QHD simulations predict significant NDR even when the original QHD
model simulations predict no NDR.
Hierarchy of Full Band Structure Modelsfor Monte Carlo Simulation
Authors: Ravaioli U. , Duncan A. , Pacelli A. , Wordelman C. , Hess K.
Published: September 2007

This paper discusses the various hierarchy levels that are possible when the full band structure
is considered. At the highest level, the scatterings are treated using complete k‐k’ transition
rates, which entail extremely memory intensive computational applications. At the
lowest level, the scattering anisotropy is neglected and the scattering rate is considered to be a
constant average value on energy isosurfaces of the bandstructure. This model is more practical
for device simulation. In between the two extremes, it is possible to design intermediate
models which preserve some essential features of both. At all levels of the band structure
hierarchy of models, there are similar issues of numerical noise, related to the sampling of
real and momentum space that the Monte Carlo method necessarily performs with a relatively
small number of particles. We discuss here computationally efficient approaches based on the
assignment of variable weights to the simulated particles, in conjunction with careful gatherscatter
procedures to split particles of large weight and combine particles of small weight.
3‐D Device Simulation Using IntelligentSolution Method Control
Authors: Kerr Daniel C. , Mayergoyz Isaak D.
Published: September 2007

In this paper, a hybrid solution method is implemented for solving the semiconductor transport
equations. The hybrid “local Newton” method consists of a combination of the fixedpoint
iteration (FPI) and Newton’s methods. The FPI technique is nearly ideally suited to
solving large, 3‐D systems of semiconductor equations on machines of limited computer
memory ; however, it has certain limitations. This motivates the local Newton method, which
coordinates the use of both the FPI and Newton’s methods, for convergence faster than either
method alone.
Formal Codesign Methodology with Multistep Partitioning
Authors: Carchiolo Vincenza , Malgeri Michele , Mangioni Giuseppe
Published: September 2007

A codesign methodology is proposed which is suitable for control‐dominated systems
but can also be extended to more complex ones. Its main purpose is to optimize the
trade‐off between hardware performance and software reprogrammability and
reconfigurability. The methodology proposed intends to cover the development of the
whole system. It deals in greater detail with the steps that can be made without the need
for any particular assumption regarding the target architecture. These steps concern
splitting up the specification of the system into a set of individually synthesizable
elements, and then grouping them for the subsequent mapping stage. In order to
decrease the complexity of each partitioning attempt, a two step algorithm is proposed,
thus permitting a wide exploration of possible solutions. The methodology is based on
the TTL language, an extension of the T‐LOTOS Formal Description Technique which
provides a large amount of operators as well as a formal basis. Finally, an example
pointing out the complete design cycle, excepting the allocation stage is provided.
MOMENTS: The Modular Monte Carlo Environment for Charge Transport Simulation,Overview and Applications
Authors: Peskin Mark , Maziar Christine
Published: September 2007

We present MOMENTS, a newly developed software library lbr Monte Carlo simulation of semiconductor devices. This library uses object‐oriented design principles to provide a flexible, extensible toolset that allows rapid development of a wide variety of Monte Carlo simulation applications. It allows concurrent simulation of multiple particle species (e.g. electrons and holes) with arbitrary user‐defined interactions between species (e.g. generation – recombination and
carrier – carrier scattering) in arbitrary geometries using either analytic or numerical bandstructure
representations. The modular design allows virtually all simulation parameters to be freely varied
across the simulation domain. MOMENTS also takes advantage of the parallelism inherent in the
ensemble Monte Carlo approach, employing a scheme that can support a wide variety of parallel
architectures with active load balancing. To demonstrate some of the library′s capabilities, we also
present preliminary results from a GaAs avalanche photodiode (APD) simulator based on
MOMENTS.
Hydrodynamic (HD) Simulation of N‐Channel MOSFET′swith a Computationally Efficient Inversion LayerQuantization Model
Authors: Wang Haihong , Shih Wei-Kai , Green Susan , Hareland Scott , Maziar Christine M. , Tasch Al. F.
Published: September 2007

A quantum mechanical treatment of electron inversion layers is incorporated in the
hydrodynamic (HD) transport model used in UT‐MiniMOS. A physically based, yet
computationally efficient, three‐subband model is implemented in the HD simulation
tool. The three‐subband model, which is based upon solutions to Schrodinger′s
equation, has the important advantage of more accurately predicting the distribution of
electrons in the inversion layers than does more conventional classical models. A more
simplified quantum mechanical model with carrier heating effects included has also been
developed. Terminal currents are calculated using these quantum mechanical models
and the comparison with results from classical calculations indicates the importance of
quantum mechanical effects in the deep submicron device simulations.
SENECA: a New Program for the Analysis of Single‐Electron Devices
Authors: Fonseca L. R. C. , Korotkov A. N. , Likharev K. K.
Published: September 2007

We describe a new and efficient method for numerical study of the dynamics and statistics of
single‐electron systems presenting arbitrary combinations of small tunnel junctions, capacitances,
and voltage sources. The method is based on the numerical solution of a master equation
describing the time evolution of the probabilities of the electric charge states of the
system, with iterative refining of the operational set of states. The method is able to describe
very small deviations from the “classical” behavior of a system, due to finite speed of applied
signals, thermal activation, and macroscopic quantum tunneling of charge (cotunneling). As
an illustration, we briefly study the leakage rate in single‐electron traps and the accuracy of
several devices (turnstile, pump, and a hybrid circuit) suitable as standards of dc current.
Convergence Properties of the Bi‐CGSTAB Method for theSolution of the 3D Poisson and 3D Electron CurrentContinuity Equations for Scaled Si MOSFETs
Authors: Vasileska D. , Gross W. J. , Kafedziski V. , Ferry D. K.
Published: September 2007

As semiconductor technology continues to evolve, numerical modeling of semiconductor
devices becomes an indispensible tool for the prediction of device characteristics.
The simple drift‐diffusion model is still widely used, especially in the study of subthreshold
behavior in MOSFETs. The numerical solution of these two equations offers
difficulties in small devices and special methods are required for the case when dealing
with 3D problems that demand large CPU times. In this work we investigate the
convergence properties of the Bi‐CGSTAB method. We find that this method shows
superior convergence properties when compared to more commonly used ILU and SIP
methods.
Interface Roughness Effects in Ultra‐Thin Tunneling Oxides
Authors: Ting D. Z.-Y. , Daniel Erik S. , Mcgill T. C.
Published: September 2007

Advanced MOSFET for ULSI and novel silicon‐based devices require the use of ultrathin
tunneling oxides where non‐uniformity is often present. We report on our
theoretical study of how tunneling properties of ultra‐thin oxides are affected by
roughness at the silicon/oxide interface. The effect of rough interfacial topography is
accounted for by using the Planar Supercell Stack Method (PSSM) which can accurately
and efficiently compute scattering properties of 3D supercell structures. Our results
indicate that while interface roughness effects can be substantial in the direct tunneling
regime, they are less important in the Fowler‐Nordheim regime.
Quantum Transport in Open Nanostructures
Authors: Zozoulenko I. V. , Berggren K.-F.
Published: September 2007

Electron transport was studied in an open square quantum dot with a dimension typical
for current experiments. A numerical analysis of the probability density distribution
inside the dot was performed which enabled us to unambiguously map the resonant states
which dominate the conductance of the structure. It was shown that, despite of the
presence of dot openings, transport through the dot is effectively mediated by just a few
(or even a single) eigenstates of the corresponding closed structure. In a single‐mode
regime in the leads, the broadening of the resonant levels is typically smaller than the
mean energy level spacing, Δ. On the contrary, in the many‐mode regime this broadening
typically exceeds Δ and has an irregular, essentially non‐Lorentzian, character. It was
demonstrated that in the latter case eigenlevel spacing statistics of the corresponding
closed system are not relevant to the averaged transport properties of the dot. This
conclusion seems to have a number of experimental as well as numerical verifications.
Time‐Dependent Solution of a Full Hydrodynamic ModelIncluding Convective Terms and Viscous Effect
Authors: Xu Deyin , Tang Ting-Wei , Kucherenko Sergei S.
Published: September 2007

Sub‐picosecond turn‐on transient behavior of ballistic diodes (N+ ‐ N ‐ N+ structures) is studied
by solving a system of time‐dependent hydrodynamic (HD) equations. Convective terms
as well as viscous effect are included in the study. The simulation result indicates that the
diode undergoes approximately one quarter of a plasma oscillation before it relaxes to the
steady‐state value through collisions.
On Rectilinear Distance‐Preserving Trees
Authors: Téllez Gustavo E. , Sarrafzadeh Majid
Published: September 2007

Given a set of terminals on the plane N = {s, ν1, …, νn}, with a source terminal s, a
Rectilinear Distance‐Preserving Tree (RDPT) T(V, E) is defined as a tree rooted at s,
connecting all terminals in N. An RDPT has the property that the length of every source
to sink path is equal to the rectilinear distance between that source and sink. A Min‐
Cost Rectilinear Distance‐Preserving Tree (MRDPT) minimizes the total wire length
while maintaining minimal source to sink linear delay, making it suitable for high
performance interconnect applications.

This paper studies problems in the construction of RDPTs, including the following
contributions. A new exact algorithm for a restricted version of the problem in one
quadrant with O(n2) time complexity is proposed. A novel heuristic algorithm, which
uses optimally solvable sub‐problems, is proposed for the problem in a single quadrant.
The average and worst‐case time complexity for the proposed heuristic algorithm are O(n3/2) and O(n3), respectively. A 2‐approximation of the quadrant merging problem is proposed. The proposed algorithm has time complexity O(α2T(n) + α3) for any constant
α > 1, where T(n) is the time complexity of the solution of the RDPT problem on one
quadrant. This result improves over the best previous quadrant merging solution which
has O(n2T(n) + n3) time complexity.

We test our algorithms on randomly uniform point sets and compare our heuristic
RDPT construction against a Minimum Cost Rectilinear Steiner (MRST) tree
approximation algorithm. Our results show that RDPTs are competitive with Steiner
trees in total wire‐length when the number of terminals is less than 32. This result makes
RDPTs suitable for VLSI routing applications. We also compare our algorithm to the
Rao‐Shor RDPT approximation algorithm obtaining improvements of up to 10% in
total wirelength. These comparisons show that the algorithms proposed herein produce
promising results.
Carrier Thermal Conductivity: Analysis and Application to Submicron‐Device Simulation
Authors: Greiner A. , Varani L. , Reggiani L. , Vecchi M. C. , Kuhn T. , Golinelli P.
Published: September 2007

Within a correlation‐function (CF) formalism, the kinetic coefficientsof charge carriers in semiconductors are studied under different conditions. For the case of linear response in equilibrium, thetransitions from the non‐degenerate to the degenerate regimes as wellas from ballistic to diffusive conditions are discussed within ananalytical model. Generalizing the method to high‐field transport innondegenerate semiconductors, the CFs are determined by Monte Carlo (MC) calculations for bulk silicon from which the appropriate thermalconductivity has been
obtained and included into the hydrodynamic code HEIELDS. For an n+nn+ submicron structure the temperatureand velocity profiles of the carriers have been calculated with HFIELDS.
A Study of Transconductance Degradation in HEMT Using a Self‐consistent Boltzmann‐Poisson‐Schrödinger Solver
Authors: Khoie R.
Published: September 2007

A self‐consistent Boltzmann‐Poisson‐Schrödinger Solver is used to study the transconductance
degradation in high electron mobility transistor (HEMT), which has extensively been
reported by both experimental [1]‐[8] and computational [9]‐[ 13] researchers. As the gate
voltage of a HEMT device is increased, its transconductance increases until it reaches a peak
value, beyond which, the transconductance is degraded rather sharply with further increase in
applied gate bias. We previously reported a two‐subband self‐consistent Boltzmann‐Poisson‐
Schrödinger Solver for HEMT. [14] We further incorporated an additional self‐consistency
by calculating field‐dependent, energy‐dependent intersubband and intrasubband
scattering rates due to ionized impurities and polar optical phonons.[15] In this work, we have
used our Boltzmann‐Poisson‐Schrödinger Solver and studied the effects of the intersubband
and intrasubband scatterings of electrons, on the transconductance of a single quantum well
HEMT device. The results of our simulations exhibit the same pattern reported by others
[1]‐[13]. We concluded that the degradation of transconductance of the device with applied
gate bias is attributed to the increased intersubband and intrasubband scattering of electrons,
and hence to the reduction of electrons velocity in the channel.
RF Performance of Si/SiGe MODFETs:A Simulation Study
Authors: Roy S. , Asenov A. , Babiker S. , Barker J. R. , Beaumont S. P.
Published: September 2007

The microwave performance potential of Si/SiGe pseudomorphic MODFETs are
studied, in comparison to state of the art InGaAs pseudomorphic HEMTs. Both devices
have equivalent structures corresponding to a physical HEMT used for calibration. We
use an RF analysis technique based on transient Monte Carlo simulations to estimate
the intrinsic noise figures, the RF figures of merit fT and fmax, and the effect of contact and gate resistances. Both devices exhibit velocity overshoot below the gate region. It is shown that the difference in noise figures and fT values can be mainly attributed to
differences in device channel velocity, fmax exhibits a strong dependence on device
contact resistance, eroding some of the performance advantage of the pseudomorphic
HEMT.
Numerical Evaluation of Iterative Schemesfor Drift‐diffusion Simulation
Authors: Patil Mahesh B. , Ravaioli Umberto , Kerkhoven Thomas
Published: September 2007

We introduce an iterative scheme to solve the drift‐diffusion device simulation problem,
which combines the Gummel iteration with the “pointwise iteration”, and then we
compare its convergence behavior with other iteration strategies, for different test cases.
Comparisons are made with the standard Gummel approach and a nonlinear multigrid
iteration. The combined “Gummel‐Pointwise” iteration has significantly better
convergence characteristics than the Gummel iteration in all cases. The cost of the
pointwise iteration varies only linearly with the number of grid points. While in terms of
CPU time for the solution the pointwise iteration is not always faster in 2‐D, in 3‐D the
combined technique becomes more and more advantageous as the grid size increases. It
is found that the nonlinear multigrid scheme is overall not as effective as the combined
iteration.
Minimum Crosstalk Vertical Layer Assignment for Three‐Layer VHV Channel Routing
Authors: Thakur Shashidhar , Chao Kai-Yuan , Wong D. F.
Published: September 2007

With the increasing density of VLSI circuits, the interconnection wires are getting
packed even closer. This has increased the effect of interaction between these wires on
circuit performance and hence, the importance of controlling crosstalk. We consider the
gridded channel routing problem where, specifically, the channel has 3 routing layers in
the VHV configuration. Given a horizontal track assignment for the nets, we present an
optimal algorithm for minimizing the crosstalk between vertical wiring segments in the
channel by finding an optimal vertical layer assignment for them. We give an algorithm
that minimizes total crosstalk between vertical wires on the same V layer on adjacent
columns of the grid in O(ν logν) time using O(ν) memory, where the channel has ν
columns. We then extend this algorithm to consider crosstalk between wires in nonadjacent
columns and between wires on different layers. Finally, we show how our
algorithms can be extended to take crosstalk tolerance specifications for nets into
account.
Phase Space Boundary Conditions and QuantumDevice Transport
Authors: Grubin H. L. , Caspar J. R. , Ferry D. K.
Published: September 2007

Device‐device interaction is described within the framework of the quantum Liouville
equation. Approximations to treating this interaction, within the framework of
alterations to phase space boundary conditions, are illustrated.
Resolution of Resonances in a General Purpose Quantum Device Simulator (NEMO)
Authors: Klimeck Gerhard , Lake Roger K. , Bowen R. Chris , Fernando Chenjing L. , Frensley William R.
Published: September 2007

Electron transport in quantum devices is governed by discrete quantum states due to electron
confinement. A crucial requirement for the modeling of quantum devices is the the numerical
identification and resolution of these quantum states. We present an algorithm utilized in our
general purpose quantum device simulator (NEMO), where we locate the resonances of the
system first and then generate the optimized grid used to integrate over the resonances. We
find this algorithm important in the modeling of coherent transport involving ultrafine resonances
and crucial for the modeling of incoherent transport.
An lnterband Tunnel Oscillator: Intrinsic Bistabilityand Hysteresis of Trapped Hole Chargein a Double‐Barrier Structure
Authors: Buot F. A.
Published: September 2007

We introduced a novel high‐frequency source based on interband tunneling. A
polarization‐induced oscillation of trapped‐hole‐charge occurs in an AlGaSb/InAs/
AlGaSb resonant tunneling device. Rate equations for Zener tunneling, polarization,
and electron‐hole recombination is used to analyze the nonlinear dynamics of this device
structure. The nonoscillatory state is unstable against the limit‐cycle operation. The
amplitude of trapped hole oscillation increases with bias, but the time‐averaged values
can be approximated by a step function. These lead to the hysteresis of the averaged
trapped hole charge in AlGaSb barrier, and to the experimental intrinsic bistability in
AlGaSb/InAs/AlGaSb resonant tunneling device. Large‐scale time‐dependent simulation
of quantum transport with interband‐tunneling dynamics is needed for the design
optimization of this novel class of oscillator useful for high‐bandwidth applications.
Bi‐Dimensional Simulation of the Simplified Hydrodynamicand Energy‐Transport Models Heter junctionSemiconductors Devices Using Mixed Finite Elements
Authors: Marrocco A. , Montarnal Ph.
Published: September 2007

We study the application of the mixed finite elements method (MFE) for the bidimensional
simulation of the simplified hydrodynamic and energy‐transport models.
The two main points are the use of entropic variables which gives a symmetric positive
definite problem and a coupled computation of the equations for electrons which
requires a generalization of the MFE method for vector valued problems. We give
numerical results on JFET and HEMT devices.
Analysis of Q0‐Independent Single‐Electron Systems
Authors: Likharev Konstantin K. , Korotkov Alexander N.
Published: September 2007

The random distribution of the background charges is a serious problem for integrated digital
single‐electron devices with capacitive coupling. We propose the new principle of operation
of the devices which does not suffer from this problem.
X3D Moving Grid Methods for Semiconductor Applications
Authors: Kuprat Andrew , Cartwright David , Gammel J. Tinka , George Denise , Kendrick Brian , Kilcrease David , Trease Harold , Walker Robert
Published: September 2007

The Los Alamos 3D grid toolbox handles grid maintenance chores and provides access
to a sophisticated set of optimization algorithms for unstructured grids. The application
of these tools to semiconductor problems is illustrated in three examples: grain growth,
topographic deposition and electrostatics. These examples demonstrate adaptive
smoothing, front tracking, and automatic, adaptive refinement/derefinement.
Recent Advances in Device Simulation Using Standard Transport Models
Authors: Baccarani G. , Rudan M. , Lorenzini M. , Sala C.
Published: September 2007

In this paper we address a number of issues related with device simulation in 3‐D, and point
out a few deficiencies which still prevent 3‐D device simulation to be widely accepted as a
standard tool for device design and optimization in an engineering environment. More specifically,
such deficiencies have to do with structure definition and mesh generation, as well as
with the computational burden which is typically associated with discretization meshes featuring
50.000 nodes or more. Next, we address the problem of validating advanced physical
models in 3‐D by means of our device simulator HFIELDS‐3D and use a flash‐EEPROM cell
manufactured at ST‐Microelectronics as a test vehicle for the validation of hot‐carrier injection
into the floating gate and Fowler‐Nordheim tunneling across the gate oxide.
Consistent Hydrodynamic and Monte‐Carlo Simulationof SiGe HBTs Based on Table Modelsthe Relaxation Times
Authors: Neinhüs B. , Decker S. , Graf P. , Bufler F. M. , Meinerzhagen B.
Published: September 2007

Good agreement between a hydrodynamic and a Monte‐Carlo device model is
demonstrated in this paper for an advanced SiGe Heterojunction Bipolar Transistor.
This result is based on two principles: 1) Extraction (from the Monte‐Carlo bulk model
under homogeneous conditions) of the relaxation times τ at discrete points of the
parameter space spanned by the Ge‐content x, doping density N, carrier temperature TC
and lattice temperature TL. 2) Modeling of the relaxation times τ(x,   TC,   TL) by
splines.
Development of a Method forDetermining the Dependence of the Electron Mobilityon the Longitudinal‐Electric Field in MOSFETs
Authors: Roldán J. B. , Gámiz F. , López-Villanueva J. A.
Published: September 2007

A new experimental method for determining the dependence of the electron mobility on
the longitudinal‐electric field has been developed. The development, validation and
explanation of this new method has been carefully carried out. We have applied this
procedure to standard submicron MOSFETs and after having obtained the mobility
dependence on both the transverse‐ and longitudinal‐electric fields we reproduced the
experimental output curves. The saturation velocity has also been calculated using the
mobility curves obtained by this new method.
Optimizing Energy During Systems Synthesis of Computer Intensive Realtime Applications
Authors: Gebotys Catherine H.
Published: September 2007

Optimizing energy during the synthesis of VLSI systems for realtime‐constrained
embedded applications is an important new problem. This paper presents a new
methodology for simultaneous scheduling and allocation of VLSI systems which
minimize estimated energy for large realtime compute intensive applications.
Minimization of estimated energy and VLSI chip area using hierarchical decomposition,
bin packing algorithms and integer linear programming techniques along with voltage
scaling is performed. Common subexpression elimination, precomputation, data
regeneration, and loop merging transformations are supported. A large complex real
industrial application, audio compression, donated by Motorola, is used to study the
energy savings using different single and multichip system implementations. Results of
synthesizing this complex application show that up to 10 times improvement in
estimated energy are attainable for only 2.7 times increase in estimated chip area.
Precomputation and other low energy transformations provided on average over 1.6
times savings in energy respectively. This research is important for industry since energy
dissipation consideration at the early stages of design is crucial for mapping high
performance applications into cost‐efficient and reliable systems.
New “Irreducible Wedge” for Scattering RateCalculations in Full‐Zone Monte Carlo Simulations
Authors: Stanley John , Goldsman Neil
Published: September 2007

To facilitate the implementation of accurate Brillouin zone integration codes for
diamond‐type semiconductors such as Si we have constructed a new “irreducible
wedge” to be used in conjunction with tetrahedral k‐space interpolations. This new
wedge, defined by the vertices (000), (100), (110) and (normalized to |X|  =  1),
spans portions of the first three Brillouin zones and contains the equivalent of 1/48 of a
Brillouin zone volume. Simple symmetry arguments may be used to establish the
equivalency of this new wedge with the standard irreducible wedge.
Spherical Harmonic Modeling of a 0.05 μmBase BJT: A Comparison with Monte Carloand Asymptotic Analysis
Authors: Chang C.-H. , Lin C.-K. , Goldsman N. , Mayergoyz I. D.
Published: September 2007

We perform a rigorous comparison between the Spherical Harmonic (SH) and Monte
Carlo (MC) methods of solving the Boltzmann Transport Equation (BTE), on a 0.05 μm
base BJT. We find the SH and the MC methods give very similar results for the energy
distribution function, using an analytical band‐structure, at all points within the tested
devices. However, the SH method can be as much as seven thousand times faster than the
MC approach for solving an identical problem. We explain the agreement by asymptotic
analysis of the system of equations generated by the SH expansion of the BTE.
Two‐dimensional Modelling of HEMTs Using Multigrids with Quantum Correction
Authors: Cole Eric A. B. , Boettcher Tobias , Snowden Christopher M.
Published: September 2007

The two‐dimensional multi‐layered HEMT is modelled isothermally by solving the
Poisson and current continuity equations consistently with the Schrödinger equation. A
multigrid method is used on the Poisson and current continuity equations while the
electron density is calculated at each level by solving the Schrödinger equation in onedimensional
slices perpendicular to the layer structure. A correction factor is introduced
which enables relatively accurate solutions to be obtained using a low number of
eigensolutions. A novel method for discretising the current density which can be
generalised to the non‐isothermal case is described. Results are illustrated using a two
layer AlGaAs‐GaAs HEMT.
Formulation of a Self‐Consistent Model for QuantumWell pin Solar Cells: Dark Behavior
Authors: Ramey S. , Khoie R.
Published: September 2007

A self‐consistent numerical simulation model for a pin single‐cell solar cell is formulated.
The solar cell device consists of a p–AlGaAs region, an intrinsic i–AlGaAs/GaAs
region with several quantum wells, and a n–AlGaAs region. Our simulator solves a
field‐dependent Schrödinger equation self‐consistently with Poisson and drift‐diffusion
equations. The field‐dependent Schrödinger equation is solved using the transfer matrix
method. The eigenfunctions and eigenenergies obtained are used to calculate the escape
rate of carriers from the quantum wells, the capture rates of carriers by the wells, the
absorption spectra in the wells, and the non‐radiative recombination rates of carriers in
the quantum wells. These rates are then used in a self‐consistent finite‐difference
numerical Poisson‐drift‐diffusion solver. We believe this is the first such comprehensive
model ever reported.
3D Parallel Monte Carlo Simulation of GaAs MESFETs
Authors: Pennathur S. , Sandalci Can K. , Koç Çetin K. , Goodnick S. M.
Published: September 2007

We have investigated three‐dimensional (3D) effects in sub‐micron GaAs MESFETs using a parallel Monte Carlo device simulator, PMC‐3D [1]. The parallel algorithm couples a standard Monte Carlo particle simulator for the Boltzmann equation with a 3D Poisson solver using spatial decomposition of the device domain onto separate processors. The scaling properties of the small signal parameters have been simulated for both the gate width in the third dimension as well as the gate length. For realistic 3D device structures, we find that the main performance bottleneck is the Poisson solver rather than the Monte Carlo particle simulator for the parallel successive overrelaxation (SOR) scheme employed in [1]. A parallel multigrid algorithm is reported and compared to the previous SOR implementation, where considerable speedup is obtained.
High‐Field Hole Transport in Strained Si and SiGe by Monte Carlo Simulation:Full Band Versus Analytic Band Models
Authors: Bufler F. M. , Graf P. , Meinerzhagen B.
Published: September 2007

Monte Carlo results are presented for the velocity‐field characteristics of holes in (i)
unstrained Si, (ii) strained Si and (iii) strained SiGe using a full band model as well as an
analytic nonparabolic and anisotropic band structure description. The full band Monte
Carlo simulations show a strong enhancement of the drift velocity in strained Si up to
intermediate fields, but yield the same saturation velocity as in unstrained Si. The drift
velocity in strained SiGe is also significantly enhanced for low fields while being
substantially reduced in the high‐field regime. The results of the analytic band models
agree well with the full band results up to medium field strengths and only the saturation
velocity is significantly underestimated.
Quantum Contributions and Violations of the Classical Law of Mass Action
Authors: Grubin H. L. , Govindan T. R.
Published: September 2007

The law of mass action refers to the product of concentration of reactants, which for a particular
material is a function only of temperature. For non‐degenerate semiconductors the law of
mass action is represented by the product NP = NCNV exp‐ EG/KBT. Through solutions to the quantum Liouville equation, it is determined that the law of mass action is generally invalid.
Electrostatic Formation of Coupled Si/SiO2Quantum Dot Systems
Authors: Hyldgaard Per , Harbury Henry K. , Porod Wolfgang
Published: September 2007

We present three‐dimensional numerical modeling results for gated Si/SiO2 quantum
dot systems in the few‐electron regime. In our simulations, the electrostatic confining
potential results from the Poisson equation assuming a self‐consistent Thomas‐Fermi
charge model. We find that a very thin SiO2 top insulating layer allows an effective
control with single‐electron confinement in quantum dots with radius less than 10nm
and investigate the detailed potential and resulting charge densities. Our three‐dimensional
finite‐element modeling tool allows future investigations of the charge
coupling in gated few‐electron quantum‐dot cellular automata.
Wave Function Scarring Effects in Open BallisticQuantum Cavities
Authors: Akis R. , Ferry D. K.
Published: September 2007

Numerical simulations have been carried out of the magneto‐transport and
corresponding wave functions of two quantum dot structures, namely the stadium
and the Sinai billiard. In our simulations, the Schrödinger equation is mapped onto a
tight‐binding lattice by replacing derivatives by finite differences, and the conductance is
calculated via the Landauer formula following the application of an iterative technique
to translate across the structure. In both structures, many of the resonance features in
the transport show scarring, that is, the amplitude of the corresponding wave functions
is highly concentrated along underlying periodic classical orbits. Our analysis indicates
that certain periodicities evident in the magneto‐transport can be associated with
particular orbits.
Modeling of Thermal Effects in Semiconductor Structures
Authors: Snowden Christopher M.
Published: September 2007

A fully coupled electro‐thermal hydrodynamic model is described which is suitable for
modelling active devices. The model is applied to the non‐isothermal simulation of
pseudomorphic high electron mobility transistors (pHEMTs). A large‐scale surface
temperature model is described which allows thermal modelling of semiconductor
devices and monolithic circuits. An example of the application of thermal modelling to
monolithic circuit characterization is given.
Total Dielectric Function Approachto the Electron Boltzmann Equation for Scatteringfrom a Two‐Dimensional Coupled Mode System
Authors: Sanborn B. A.
Published: September 2007

The nonequilibrium total dielectric function lends itself to a simple and general method for
calculating the inelastic collision term in the electron Boltzmann equation for scattering from
a coupled mode system. Useful applications include scattering from plasmon‐polar phonon
hybrid modes in modulation doped semiconductor structures. This paper presents numerical
methods for including inelastic scattering at momentum‐dependent hybrid phonon frequencies
in the low‐field Boltzmann equation for two‐dimensional electrons coupled to bulk phonons.
Results for electron mobility in GaAs show that the influence of mode coupling and
dynamical screening on electron scattering from polar optical phonons is stronger for two
dimensional electrons than was previously found for the three dimensional case.
Application of the Wigner‐Function Formulation toMesoscopic Systems in Presence of Electron‐PhononInteraction
Authors: Jacoboni C. , Abramo A. , Bordone P. , Brunetti R. , Pascoli M.
Published: September 2007

A theoretical and computational analysis of the quantum dynamics of charge carriers in
presence of electron‐phonon interaction based on the Wigner function is here applied to
the study of transport in mesoscopic systems. Numerical applications are shown for a) a
wave packet scattering with phonons while crossing a potential profile and b) electrons
scattering with phonons in a finite device with open boundary conditions.
Boundary Condition for the Modeling of Open‐circuitedDevices in Non‐equilibrium
Authors: Parks Joseph W. , Brennan Kevin F.
Published: September 2007

A boundary condition specifically designed to model open‐circuited devices in a
macroscopic device simulator is introduced. Other simulation techniques have relied on
an external circuit model to regulate the current flow out of a contact thus allowing the
potential to remain the controlled variable at the boundary. The limitations of these
methods become apparent when modeling open‐circuited devices with an exceptionally
small or zero output current. In this case, using a standard ohmic‐type Dirichlet
boundary condition would not yield satisfactory results and attaching the device to an
arbitrarily large load resistance is physically and numerically unacceptable. This
proposed condition is a true current controlled boundary where the external current is
the specified parameter rather than the potential. Using this model, the external current
is disseminated into electron and hole components relative to their respective
concentration densities at the contact. This model also allows for the inclusion of
trapped interface charge and a finite surface recombination velocity at the contact.

An example of the use of this boundary condition is performed by modeling a silicon
avalanche photodiode operating in the flux integrating mode for use in an imaging
system. In this example, the device is biased in steady‐state to just below the breakdown
voltage and then open‐circuited. The recovery of the isolated photodiode back to its
equilibrium condition is then determined by the generation lifetime of the material, the
quantity of signal and background radiation incident upon the device, and the impact
ionization rates.
Macroscopic Device Simulation of InGaAs/InP Based Avalanche Photodiodes
Authors: Parks Joseph W. , Brennan Kevin F. , Tarof Larry E.
Published: September 2007

In this paper, we analyze, based on a two‐dimensional drift‐diffusion simulation, how variations
in the structural components of an InGaAs/InP separate absorption, grading, charge, and
multiplication photodiode (SAGCM) alter its performance. The model is employed in conjunction
with experimental measurements to enhance the understanding of the device performance.
Calibration of the model to the material system and growth technique is performed
via the analysis of a simpler, alternate structure. Excellent agreement between the calculated
results and experimental measurements of the breakdown voltage, dark current, mesa punchthrough
voltage, photoresponse, and gain are obtained.
Optical and Electronic Properties of Semiconductor2D Nanosystems: Self‐consistentTight‐binding Calculations
Authors: Reale Andrea , Carlo Aldo Di , Pescetelli Sara , Paciotti Marco , Lugli Paolo
Published: September 2007

A tight‐binding models which account for band mixing, strain and external applied
potentials in a self‐consistent fashion has been developed. This allows us to describe
electronic and optical properties of nanostructured devices beyond the usual envelope
function approximation. This model can be applied to direct and indirect gap
semiconductors thus allowing for instance the self‐consistent calculation of band profile
and carrier control in pseudomorphic InGaAs/GaAs HEMTs and SiGe/Si MODFETs.