1,721,093 research outputs found
Device Modeling
No full textIn this chapter we describe the modeling approaches developed for the simulation of germanium devices. The main focus will be on metal-insulator-semiconductor (MIS) devices, with particular attention on germanium-on-insulator (GOI) structures. Most of the approaches were originally developed for silicon devices, and thus we will describe them briefly, stressing the differences between Si and Ge and how they translate in different modeling requirements.
The chapter is organized according to a “bottom-up” structure, beginning with Section 9.2 which describes the main differences between the basic properties of Ge and Si, and then spanning from band-structure calculation up to the determination of the drain current in MIS devices for both n-channel and p-channel transistors. However, so far, most of the models have been developed for n-channel devices and cannot be easily extended to p-channel transistors. This is reflected also in the material presented in this chapter, which is more complete and richer of examples for n-channel than it is for p-channel transistors.
Section 9.3 is devoted to band-structure calculation. Since the main interest is in MIS devices, where carriers are quantized in a 2D inversion layer, a relevant fraction of the section is focused on the calculation of the energy states in 2D systems.
In the semi-classical physical framework that we will consider hereafter, the transport modeling is essentially based on the Boltzmann transport equation (BTE), whose general solution is
very complex because the scattering integrals make the stationary BTE an integral–differential equation in a multi-dimensional space of the phases (which has six dimensions for a bulk semiconductor and four dimensions for a 2D inversion layer). A dramatic simplification is
obtained by neglecting the scattering term, which leads to the ballistic transport regime. This simplified approach is mostly useful to investigate the upper-limits of the performance that can be attained with a device structure, so that it can be used for a preliminary investigation of the possible benefits related to new device structures, such as Ge channel Metal-oxidesemiconductor
field effect transistor (MOSFETs). This aspect is described in Section 9.4, where comparisons between Si and Ge devices are provided.
The solution of the BTE beyond the ballistic approximation is considered in Section 9.5, starting from approximate solutions such as the Drift-Diffusion approach, and then considering more accurate approaches, such as the Monte-Carlo (MC) method.
Finally, in Section 9.6 we will draw our conclusion and propose a “roadmap” for the forthcoming activities in the field of the simulation of advanced Ge devices
Monte Carlo Simulation of deca-nanometer MOSFETs for Analog/Mixed-Signal and RF applications
No full textIn this work, a Monte-Carlo simulator including the most relevant scattering mechanisms and quantum corrections to the potential, already extensively applied to the DC analysis of ultra-short devices and upgraded in order to allow RF device analysis, is applied to the investigation of the RF performance of bulk MOSFETs designed according to the prescriptions of the 2005 ITRS Roadmap and of a 53 nm ultra-thin-body (UTB) single-gate (SG) SOI MOSFET.
Original contributions consist in the analysis of the signal-delay build-up along the channel and investigation of the scaling properties of the parameters of the AC equivalent circuit, transition frequency FT and 3dB bandwidth of the voltage gain in common-source configuration.
The effects of ballistic transport and their impact on the AC figures of merit are investigated for short UTB Double-Gate (DG) MOSFETs
Monte-Carlo Analysis of Signal Propagation Delay and AC Performance of Decananometric Bulk and Double-Gate MOSFETs
No full textA time-dependent simulation procedure has been implemented in a state of the art Monte Carlo device simulator that includes quantum corrections and applied to the evaluation of the RF performance of bulk and ultra-thin-body double-gate (UTB-DG) MOSFETs with LG = 25 nm.
The analysis focuses on the evaluation of the signal delay along the channel and of the admittance matrix at the device terminals.
The performance of the bulk and UTB-DG MOSFETs are compared; the latter provides a significantly larger transition frequency (FT), due to the larger trans-conductance and much lower total drain capacitance, thanks to suppressed junction capacitance
Monte Carlo modeling of nanometer scale MOSFETs
No full textRecent developments in the Monte Carlo method for the simulation of semi-classical carrier transport in nano-MOSFETs include the treatment of quantum-mechanical effects in the simulation (using either the Multi-Subband approach or quantum corrections to the electrostatic potential). In this paper, after reviewing recent progress in this field, selected applications are presented, including the analysis of quasi-ballistic transport, the determination of the RF characteristics of deca-nanometric MOSFETs, and the study of non-conventional device structures and channel materials
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
The impact of longitudinal nonuniform fin-thickness on quasi-ballistic transport in FinFETs
No full textThe impact of fin-thickness nonuniformities on carrier transport in FinFETs is analyzed with a quasi-ballistic transport model based on the multi-subband Monte Carlo technique. Silicon channels featuring thickness constrictions or enlargements show subband energy variations due to the changes in vertical quantization along the fin. We found that the impact on the on-current is larger when the nonuniformities are located close to the virtual source of the device. Furthermore, the sensitivity of on-current to thickness nonuniformity is essentially the same when considering different crystal orientations. Comparison with drift-diffusion simulations reveals quantitative and qualitative differences in the predicted drain current trends of these nanoscale, quasi-ballistic MOS devices
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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