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 &#964; at discrete points of theparameter space spanned by the Ge-content x, doping density N, carrier temperature <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>T</mml:mi><mml:mi>C</mml:mi></mml:msub></mml:mrow></mml:math>and lattice temperature <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>T</mml:mi><mml:mi>L</mml:mi></mml:msub><mml:mo>.</mml:mo><mml:mtext>&#x2009;</mml:mtext><mml:mn>2</mml:mn></mml:mrow></mml:math>) Modeling of the relaxation times <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>&#x03C4;</mml:mi><mml:mrow><mml:mo>(</mml:mo><mml:mrow><mml:mi>x</mml:mi><mml:mo>,</mml:mo><mml:mtext>&#x2009;</mml:mtext><mml:mtext>&#x2009;</mml:mtext><mml:msub><mml:mi>T</mml:mi><mml:mi>C</mml:mi></mml:msub><mml:mo>,</mml:mo><mml:mtext>&#x2009;</mml:mtext><mml:mtext>&#x2009;</mml:mtext><mml:msub><mml:mi>T</mml:mi><mml:mi>L</mml:mi></mml:msub></mml:mrow><mml:mo>)</mml:mo></mml:mrow></mml:mrow></mml:math> bysplines.

B.  Neinh&#252;s

S.  Decker

P.  Graf

F. M. Bufler

B.  Meinerzhagen

Consistent Hydrodynamic and Monte-Carlo Simulationof SiGe HBTs Based on Table Modelsthe Relaxation Times

Non-local electron transport in nMOSFET inversion layers has been studied by Monte
Carlo (MC) simulations. Inversion layer quantization has been explicitly included in the
calculation of density of states and scattering rate for low-energy electrons while bulk
band structure is used to describe the transport of more energetic electrons. For
uniform, high-lateral field conditions, the effects of quantization are less pronounced
due to the depopulation of electrons in the lower-lying subbands. On the other hand,
Monte Carlo results for carrier transport in spatially varying lateral fields (such as those
in the inversion layer of MOSFETs) clearly indicate that depopulation of the low-lying
subbands is less evident in the non-local transport regime. Quasi-2D simulations have
shown that, at high transverse effective field, the inclusion of a quantization domain
does have an impact on the calculated spatial velocity transient.

Wei-Kai Shih

Srinivas Jallepalli

Mahbub Rashed

Christine M. Maziar

Al. F. Tasch Jr.

Study of Electron Velocity Overshoot in NMOS
Inversion Layers

A self-consistent numerical simulation model for a pin single-cell solar cell is formulated.The solar cell device consists of a p&#8211;AlGaAs region, an intrinsic i&#8211;AlGaAs/GaAsregion with several quantum wells, and a n&#8211;AlGaAs region. Our simulator solves afield-dependent Schr&#246;dinger equation self-consistently with Poisson and drift-diffusionequations. The field-dependent Schr&#246;dinger 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.

S.  Ramey

R.  Khoie

Formulation of a Self-Consistent Model for QuantumWell pin Solar Cells: Dark Behavior

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.

Christopher M. Snowden

Modeling of Thermal Effects in Semiconductor Structures

The two-dimensional multi-layered HEMT is modelled isothermally by solving thePoisson and current continuity equations consistently with the Schr&#246;dinger 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 Schr&#246;dinger 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.

Eric A. B. Cole

Tobias  Boettcher

Two-dimensional Modelling of HEMTs Using Multigrids with Quantum Correction

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.

C. Jacoboni

A. Abramo

P. Bordone

R. Brunetti

M. Pascoli

Application of the Wigner-Function Formulation to
Mesoscopic Systems in Presence of Electron-Phonon
Interaction

The use of a wavelet basis can lead to efficient methods for performing ab initio
electronic structure calculations of inherently localized structures. In this work wavelets
are used to construct an adaptive basis which is optimized dynamically throughout the
calculation. The computational effort of such a method should scale linearly with the
number of basis functions. The adaptive basis is tested for the case of bulk Si using only
a local s-pseudopotential.

D. A. Richie

P. von Allmen

K. Hess

Richard M. Martin

Electronic Structure Calculations Using
An Adaptive Wavelet Basis

The importance of 2-dimensional (2D) features of carriers in Si MOSFETs on the deviceperformance is re-examined experimentally and theoretically from the viewpoint of low-fieldmobility, velocity in high tangential fields and the inversion-layer capacitance. It isconfirmed that low-field mobility and inversion-layer capacitance can be understoodwell in terms of the 2D subbands and the 2D carrier transport. In order to obtain fully-quantitativeunderstanding of low-field mobility, however, it is still necessary to moreaccurately determine the amount of the scattering parameters in the inversion layer. Onthe other hand, saturation velocity is considered to be less influenced by the 2Dquantization, while it is found experimentally that saturation velocity is slightlydependent on surface carrier concentration.According to the knowledge of 2-dimensional carrier transport in Si inversion layer,an effective way to have higher current drive is to increase the occupancy of the 2-foldvalleys, which have lower conductivity mass, on a (100) surface. From this viewpoint,two device structures, strained Si MOSFETs and SOI MOSFETs with ultra-thin SOIfilms, are introduced and the behavior of low-field mobility is analyzed through thecalculations of the subband structures and phonon-limited mobility.

Shin-Ichi  Takagi

Two-dimensional Carrier Transport in Si MOSFETs

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.

Andrea  Reale

Aldo Di Carlo

Sara  Pescetelli

Marco  Paciotti

Paolo  Lugli

Optical and Electronic Properties of Semiconductor2D Nanosystems: Self-consistentTight-binding Calculations

We examine an alternative layout geometry for the quantum cellular automata (QCA)architecture. In the traditional QCA geometry, all of the cells are placed in a singleplane, so that each cell interacts with a particular neighbor only along one of its edges.By rotating the cells out of the plane, we make it possible for neighbors to interact alongall four edges at once. This increased interaction leads to a more bistable cell-cellresponse function and a 50&#37; higher excitation energy. We also present a majority logicgate designed using three-dimensional cells.

Paul G. Krause

Rachel M. Mueller

P. Douglas Tougaw

Janelle M. Weidner

An Alternative Geometry for Quantum Cellular Automata

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