1,721,031 research outputs found
Charge transport models for amorphous chalcogenides
No full textThe chapter addresses the issue of transport models applied to the
amorphous chalcogenides which, in the last decades, have acquired
importance in the design and manufacture of solid-state memories. After
an introductory part where the main properties of the materials are
outlined, ab initio atomistic, and semiclassical computational approaches
for the study of the atomic structure and the features of electronic states
of chalcogenides are briefly illustrated. This part is concluded by a
description of the resistance-drift phenomenon and of how the simulation
approaches contributed to the comprehension of the underlying physics.
The successive section summarizes a variety of physical models
and numerical methods useful for describing charge transport in the
materials. The issue is developed in the two subsequent sections,
dealing with microscopic and macroscopic models, respectively. The
first section of the pair addresses the trap-limited transport model in the
hydrodynamic form and discusses a 3D network of randomly placed
traps. Specific issues, like detrapping due to electron-electron interaction
and the probability of inter-trap transitions, are addressed here. Finally,
ab initio quantum models for ultrascaled devices are illustrated
The Semiconductor Model Solved by the Numerov Process over a Non-Uniform Grid
No full textThe Numerov Process (NP) provides the solution of some classes of ODEs with an accuracy much superior to that of the standard finite-difference or box-integration methods. The original formulation of NP requires a uniform grid, which is a drawback for applications to, e.g., the semiconductor-device equations. Purpose of this work is showing how a method for extending NP to a non-uniform grid is applied to the solution of the drift-diffusion model. The method keeps the fifth-order accuracy of the original NP. In the multi-dimensional case, the variable transformation illustrated in the paper is found beneficial also when standard solution schemes are used; in fact, it makes the current-density vector well defined within each grid element
The Numerov process over a non-uniform grid
Full text linkThe Numerov process is a solution method applicable to some classes of differential equations, that provides an error term of the fifth order in the grid size with a computational cost comparable to that of the finite-difference scheme. In the original formulation of the method, a uniform grid size is required; the paper shows a procedure for extending its applicability to a non-uniform grid in one dimension. The effectiveness of the procedure is tested on a model problem, and comparisons with other methods are carried out. Finally, it is shown how to extend the applicability of the method to a larger class of equations; among these, the mathematical model of semiconductor devices is important in view of its applications to the integrated-circuit technology
Springer Handbook of Semiconductor Devices
No full textNo other class of materials than semiconductors, since the early identification of their electrical,
optical, and thermal properties at the beginning of the nineteenth century, has been so deeply
investigated and used to design all kinds of devices. The first theoretical models about the
physics of semiconductors, based on quantum-mechanical grounds, fueled the design of solidstate
diodes and transistors; these, in turn, have opened new horizons to electronics, computer
science, and sensors, and have greatly impacted the global market with annual revenues of the
order of 500 billion US dollars in the present days.
In turn, semiconductor companies pushed ahead the search of new semiconductor materials
and structures suited for specific applications, and urged academia and the industry’s R&D
toward the elaboration of more and more powerful simulation tools to inquire about the
effects of miniaturization, interfaces, and doping on device performance and reliability, or
to benchmark specific semiconductor properties before investing resources in expensive
innovations of the production lines.
All the above justify the effort of putting together, in this Springer Handbook of Semiconductor
Devices, many cross-disciplinary competences about present-day and near-future
semiconductor devices, namely modern concepts in solid-state physics, material science,
growth and process technology, device design, and advanced simulation strategies.
When we speak about semiconductor devices, what we consider “future” is very often
already “present time” somewhere in the world. Thus, this handbook not only includes the most
recent progress in research and technology of conventional semiconductor devices and sensors
but enlarges its view to include some specific topics related to new materials and designs,
presently at the frontier between science and technology, nonetheless suitable to be employed
in the next-generation semiconductor-technology challenges.
The handbook is organized in four parts: 1. Technological Aspects; 2. Basic Devices and
Applications; 3. New-Generation Devices and Architectures; 4 Modeling. Almost 100 leading
scientists from both academia and industry were invited to contribute to the 45 chapters of the
handbook, which has been conceived for professionals and practitioners, material scientists,
physicists, and electrical engineers working at universities, industrial R&D, and production.
Each chapter is self-contained and refers to related topics treated in other chapters when
necessary, so that the reader interested in a specific subject can easily identify a personal path
through the massive contents of the handbook.
We are very grateful to all the authors who joined this ambitious enterprise, to the referees
who generously contributed to improve the quality of the final outcome, to Springer’s editors
who patiently followed ourwork step by step, and, last but not least, to Prof. Chihiro Hamaguchi
(Osaka University) and Prof. Herman Maes (KU Leuven and imec) for providing forewords
based on their long-term experience in the field of semiconductor science and technology
Density of states and group velocity of electrons in SiO2 calculated from a full band structure
No full textThe full band structure of SiO2 has been determined in order to calculate parameters that are necessary for the description of carrier transport. Ab initio calculations of the density of states and group velocity for the conduction bands of SiO2 are worked out as a function of energy. Four different crystal structures of SiO2 are investigated, which are known to be built up by the same fundamental unit, namely, the SiO4 tetrahedron: they are the α- and β-quartz and the α- and β-cristobalite. All of them are polymorphs of silica. The conduction bands are calculated by means of two different techniques: the Hartree-Fock method and density-functional theory. The different features of the two methods are examined. Eight energy bands are used to calculate the density of states and group velocity for the energies of interest. Based on such calculations, the relevant scattering mechanisms have been modeled to determine the microscopic relaxation times. This in turn allows for the solution of the Boltzmann transport equation in the coordinate and energy space, which eventually leads to the calculation of macroscopic quantities such as carrier concentration, average velocity, and average energy. Examples are given of calculated electron mobility and average energy, along with comparisons with experimental results available in the literature
Hole density of states and group velocity in SiO2
No full textDensity of states and group velocity for the valence bands of SiO2 are worked out as a function of energy. The purpose is to provide reliable parameters for the calculation of hole transport within gate oxides, which is acquiring more relevance in view of the application to advanced MOS devices. It is shown that the applicability of the effective-mass concept to hole transport in SiO2 is much more restricted than in other materials. © 2003 The American Physical Society
Solution of the semiconductor-device equations by the numerov process
Full text linkThe one-dimensional form of some types of differential equations that appear in the modeling of solid-state devices, like, e.g., the Poisson and Schrödinger equations, can be solved numerically using the Numerov Process (NP). The accuracy of NP is superior by at least two orders of magnitude to that of commonly-used solution methods like, e.g., the finite-difference one. Another advantage of NP is that the increase in computational cost is modest. This paper investigates the possibility of extending the applicability of NP to the whole set of equations that constitute the mathematical model of semiconductor devices. It shows that the charge-continuity and charge-transport equations can be recast in a form suitable for NP. The performance of the method is tested on an n+-n-n+ device, and the extension of the approach to the two-dimensional transport problem is worked out
Homogeneous transport in silicon dioxide using the spherical-harmonics expansion of the BTE
No full textThe spherical-harmonics expansion (SHE) method is employed to solve the Boltzmann transport equation (BTE) in SiO2. Both the polar and nonpolar electron-phonon scattering mechanisms are considered. A number of macroscopic transport properties of electrons in SiO2 are worked out in the steady-state regime for a homogeneous bulk structure. The analysis shows a good agreement in comparison with experiments in the low-field regime
Temperature dependence of the electron and hole scattering mechanisms in silicon analyzed through a full-band, spherical-harmonics solution of the BTE
No full textBy adopting the solution method for the BTE based on the spherical-harmonics expansion (SHE) [1], and using the full-band structure for both the electron and valence band of silicon [2], the temperature dependence of a number of scattering mechanisms has been modeled and implemented into the code HARM performing the SHE solution. Comparisons with the experimental mobility data show agreement over a wide range of temperatures. The analysis points out a number of factors from which the difficulties encountered in earlier investigations seemingly originate, particularly in the case of hole mobility
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