Now-a-days SiGe HBTs are surpassing even the fastest III-V production devices
in the high–speed orbit. The state-of-art in simulation of silicon germanium semiconductor
devices is presented in this paper. A comprehensive course of action to model the device
parameter characterization of High Frequency 0.1μm SiGe HBT is depicted which is based on
the technique of direct parameter extraction. With the help of S-, Y- and Z- parameters, the
equivalent circuit parameters have been extracted in a faultless approach. The intrinsic and the
extrinsic elements of model are obtained using a direct extraction method that assists to find
out the base resistance from the Z- parameters. In this, the issues entailed in simultaneous
optimization of fmax and fT and related optimization of base resistance as well as junction
capacitance are addressed. The device characteristics of the SiGe HBT are found much
advance to those of III–V semiconductor devices. A corroboration of objective validity of the
modeling scheme and the extraction of parameter is accomplished in the form of S-parameters.
These results have been validated using a viable numerical device simulator ATLAS from
Silvaco International.
Range Extended Second Order Digital Phase Locked LoopIDES Editor
A new structure of second order digital phase
locked loop (DPLL) called modified second order DPLL
(MSODPLL) has been proposed. The phase error
dynamics of a conventional second order DPLL
(CSODPLL) and that of a MSODPLL have been studied
using digital computers. Ranges of initial conditions
leading to the phase locking condition were determined
from computer simulation of both conventional and
modified second order DPLL Using these observations
the larger frequency acquisition range (FAR) of the
MSODPLL compared to the CSODPLL has been
established.
Range Extended Second Order Digital Phase Locked LoopIDES Editor
A new structure of second order digital phase
locked loop (DPLL) called modified second order DPLL
(MSODPLL) has been proposed. The phase error
dynamics of a conventional second order DPLL
(CSODPLL) and that of a MSODPLL have been studied
using digital computers. Ranges of initial conditions
leading to the phase locking condition were determined
from computer simulation of both conventional and
modified second order DPLL Using these observations
the larger frequency acquisition range (FAR) of the
MSODPLL compared to the CSODPLL has been
established.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
GPR Probing of Smoothly Layered Subsurface Medium: 3D Analytical ModelLeonid Krinitsky
An analytical approach to GPR probing of a
horizontally layered subsurface medium is developed, based on the coupled-wave WKB approximation. An empirical model of current in dipole transmitter antenna is used.
Genetic Algorithms and Genetic Programming for Multiscale Modelingkknsastry
Effective and efficient multiscale modeling is essential to advance both the science and synthesis in a wide array of fields such as physics, chemistry, materials science, biology, biotechnology and pharmacology. This study investigates the efficacy and potential of using genetic algorithms for multiscale materials modeling and
addresses some of the challenges involved in designing competent algorithms that solve hard problems quickly, reliably
and accurately.
What Makes Training Multi-modal Classification Networks Hard? ppttaeseon ryu
[딥러닝 논문읽기 모임 100번째]
What Makes Training Multi-modal Classification Networks Hard?
안녕하세요! 우선 '딥러닝 논문 읽기 모임'의 영상이 드디어 100번째 업로드를 하였습니다! 그동안 계속해서 관심을 보내주시고 청강 방 등 다양한 경로로 참여해주신 구성원분들, 또 구독자님들 감사드립니다. 앞으로 계속해서 딥러닝 현업/전공자분들께 도움이 되는 논문 영상을 업로드 하도록 하겠습니다!
오늘 소개해 드릴 100번째 영상은, What Makes Training Multi-modal Classification Networks Hard? 라는 제목의 논문입니다.
multi modal이란, 다양한 모델들을 합하여, 성능을 올리는 방법인데요, 예를 들어, 특허 문서나 금융 데이터 관련된 문서인 경우 텍스트에만 의존해서 분류를 시도하는 건 어려운 문제들이 많이 존재합니다. 실제로 사람들도 유사한 특허인지, 이 사람의 금융 관련된 실적을 평가하고 판단할 때는 텍스트 데이터에만 의존하는 것이 아닌, 음성+텍스트, 텍스트+이미지와 같은 많은 데이터를 활용하는 게 일반적입니다. 하지만 많은 멀티모달이 두 가지의 모델에서 feature를 뽑아내고 학습하는 도중에 overfitting과 같은 문제에 부딪히고 좋은 성능을 내지는 못하였습니다. 오늘 업로드된 논문은 G-blend라는 기법을 사용하여 이러한 문제를 해결하였고 높은 정확도를 기록하였습니다
오늘도 많은 관심 감사드리며! 앞으로도 잘 부탁드립니다.
https://youtu.be/ZjDRVgA9F1I
Plasmon Enhanced Internal Quantum Efficiency of CdSe/ZnS Quantum Dotsijrap
The effects of surface plasmon oscillations on the radiative recombination rate and internal quantum efficiency of silver coated CdSe/ZnS quantum dots imbedded in quartz matrix is studied theoretically and
numerically. The analysis is carried out by introducing the local field enhancement factor for the description of the dielectric function of the quantum dots together with the modified Drude model for the metal-coat that takes into account the effects of interband transitions and the size dependent damping
parameter. It is found out that the internal quantum efficiency of photoluminescence emission of the metalcoated CdSe/ZnS quantum dots is enhanced by about 5-folds compared with the quantum dots without metal-coat. Moreover, increasing the metal fraction of the coated CdSe/ZnS quantum dots from 0.80 to 0.92 results in a significant increase of the intensity that is accompanied by a blue-shift of the quantum efficiency curves. The results obtained can be utilized in the design and fabrication of optoelectronic devices that require high intensity of photoluminescence emission.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
Segmentation Based Multilevel Wide Band Compression for SAR Images Using Coif...CSCJournals
Synthetic aperture radar (SAR) data represents a significant resource of information for a large variety of researchers. Thus, there is a strong interest in developing data encoding and decoding algorithms which can obtain higher compression ratios while keeping image quality to an acceptable level. In this work, results of different wavelet-based image compression and segmentation based wavelet image compression are assessed through controlled experiments on synthetic SAR images. The effects of dissimilar wavelet functions, number of decompositions are examined in order to find optimal family for SAR images. The choice of optimal wavelets in segmentation based wavelet image compression is coiflet for low frequency and high frequency component. The results presented here is a good reference for SAR application developers to choose the wavelet families and also it concludes that wavelets transform is rapid, robust and reliable tool for SAR image compression. Numerical results confirm the potency of this approach.
Numerical investigation of the performance of AlGaN/GaN/BGaN double-gate dou...IJECEIAES
In this work, we examine the direct-current (DC) behavior and the radio frequency (RF) performance of both single-gate simple-channel (SGSC), single-gate double-channel (SGDC) and double-gate double-channel (DGDC) AlGaN/GaN/BGaN high electron mobility transistor (HEMT) with BGaN back-barriers consist of 250 nm gate length. Using technology computer aided design (TCAD) Silvaco, our isothermal simulation results reveal that the proposed structure of double-gate double-channel HEMT with BGaN back-barriers (DGDCBB HEMT) increases electron concentration and consequently the saturation drain current, breakdown voltage, the transconductance. On the other hand, decreases the gate leakage current compared to a conventional HEMT and to a double-channel HEMT back-barriers. Furthermore, the proposed double-gate double-channel backbarrier HEMT device shows good cutoff frequency (94 GHz) and a maximum oscillation frequency (170 GHz). These results suggest that double-gate double channel HEMT back-barriers could be useful for high frequency and high-power microwave applications.
Dual Band to Wideband Pentagon-shaped Patch Antenna with Frequency Reconfigur...IJECEIAES
A dual band to wideband reconfigurable pentagon-shaped antenna with EBG unit cell is proposed. A minimal number of two EBG unit cell is deployed to realize frequency reconfigurable mechanism. By varying the state of the EBG the antenna is capable to change its dual band operation to wideband alternately. There are three cases that have been analysed, first case is the EBG incorporated antenna with ideal and second is with the active EBG. Subsequently, the third cases is the fabricated ideal EBG incorporated antenna. The dual band operation is at 1.8 GHz and 5.2 GHz while the wide band from 1.6 GHz to 2.37 GHz (770 MHz). The proposed reconfigurable antenna is suitable to be implemented for LTE (1.6 GHz), Wi-Fi (5.2 GHz), WiMAX (2.3 GHz) and cognitive radio application.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
GPR Probing of Smoothly Layered Subsurface Medium: 3D Analytical ModelLeonid Krinitsky
An analytical approach to GPR probing of a
horizontally layered subsurface medium is developed, based on the coupled-wave WKB approximation. An empirical model of current in dipole transmitter antenna is used.
Genetic Algorithms and Genetic Programming for Multiscale Modelingkknsastry
Effective and efficient multiscale modeling is essential to advance both the science and synthesis in a wide array of fields such as physics, chemistry, materials science, biology, biotechnology and pharmacology. This study investigates the efficacy and potential of using genetic algorithms for multiscale materials modeling and
addresses some of the challenges involved in designing competent algorithms that solve hard problems quickly, reliably
and accurately.
What Makes Training Multi-modal Classification Networks Hard? ppttaeseon ryu
[딥러닝 논문읽기 모임 100번째]
What Makes Training Multi-modal Classification Networks Hard?
안녕하세요! 우선 '딥러닝 논문 읽기 모임'의 영상이 드디어 100번째 업로드를 하였습니다! 그동안 계속해서 관심을 보내주시고 청강 방 등 다양한 경로로 참여해주신 구성원분들, 또 구독자님들 감사드립니다. 앞으로 계속해서 딥러닝 현업/전공자분들께 도움이 되는 논문 영상을 업로드 하도록 하겠습니다!
오늘 소개해 드릴 100번째 영상은, What Makes Training Multi-modal Classification Networks Hard? 라는 제목의 논문입니다.
multi modal이란, 다양한 모델들을 합하여, 성능을 올리는 방법인데요, 예를 들어, 특허 문서나 금융 데이터 관련된 문서인 경우 텍스트에만 의존해서 분류를 시도하는 건 어려운 문제들이 많이 존재합니다. 실제로 사람들도 유사한 특허인지, 이 사람의 금융 관련된 실적을 평가하고 판단할 때는 텍스트 데이터에만 의존하는 것이 아닌, 음성+텍스트, 텍스트+이미지와 같은 많은 데이터를 활용하는 게 일반적입니다. 하지만 많은 멀티모달이 두 가지의 모델에서 feature를 뽑아내고 학습하는 도중에 overfitting과 같은 문제에 부딪히고 좋은 성능을 내지는 못하였습니다. 오늘 업로드된 논문은 G-blend라는 기법을 사용하여 이러한 문제를 해결하였고 높은 정확도를 기록하였습니다
오늘도 많은 관심 감사드리며! 앞으로도 잘 부탁드립니다.
https://youtu.be/ZjDRVgA9F1I
Plasmon Enhanced Internal Quantum Efficiency of CdSe/ZnS Quantum Dotsijrap
The effects of surface plasmon oscillations on the radiative recombination rate and internal quantum efficiency of silver coated CdSe/ZnS quantum dots imbedded in quartz matrix is studied theoretically and
numerically. The analysis is carried out by introducing the local field enhancement factor for the description of the dielectric function of the quantum dots together with the modified Drude model for the metal-coat that takes into account the effects of interband transitions and the size dependent damping
parameter. It is found out that the internal quantum efficiency of photoluminescence emission of the metalcoated CdSe/ZnS quantum dots is enhanced by about 5-folds compared with the quantum dots without metal-coat. Moreover, increasing the metal fraction of the coated CdSe/ZnS quantum dots from 0.80 to 0.92 results in a significant increase of the intensity that is accompanied by a blue-shift of the quantum efficiency curves. The results obtained can be utilized in the design and fabrication of optoelectronic devices that require high intensity of photoluminescence emission.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
Segmentation Based Multilevel Wide Band Compression for SAR Images Using Coif...CSCJournals
Synthetic aperture radar (SAR) data represents a significant resource of information for a large variety of researchers. Thus, there is a strong interest in developing data encoding and decoding algorithms which can obtain higher compression ratios while keeping image quality to an acceptable level. In this work, results of different wavelet-based image compression and segmentation based wavelet image compression are assessed through controlled experiments on synthetic SAR images. The effects of dissimilar wavelet functions, number of decompositions are examined in order to find optimal family for SAR images. The choice of optimal wavelets in segmentation based wavelet image compression is coiflet for low frequency and high frequency component. The results presented here is a good reference for SAR application developers to choose the wavelet families and also it concludes that wavelets transform is rapid, robust and reliable tool for SAR image compression. Numerical results confirm the potency of this approach.
Numerical investigation of the performance of AlGaN/GaN/BGaN double-gate dou...IJECEIAES
In this work, we examine the direct-current (DC) behavior and the radio frequency (RF) performance of both single-gate simple-channel (SGSC), single-gate double-channel (SGDC) and double-gate double-channel (DGDC) AlGaN/GaN/BGaN high electron mobility transistor (HEMT) with BGaN back-barriers consist of 250 nm gate length. Using technology computer aided design (TCAD) Silvaco, our isothermal simulation results reveal that the proposed structure of double-gate double-channel HEMT with BGaN back-barriers (DGDCBB HEMT) increases electron concentration and consequently the saturation drain current, breakdown voltage, the transconductance. On the other hand, decreases the gate leakage current compared to a conventional HEMT and to a double-channel HEMT back-barriers. Furthermore, the proposed double-gate double-channel backbarrier HEMT device shows good cutoff frequency (94 GHz) and a maximum oscillation frequency (170 GHz). These results suggest that double-gate double channel HEMT back-barriers could be useful for high frequency and high-power microwave applications.
Dual Band to Wideband Pentagon-shaped Patch Antenna with Frequency Reconfigur...IJECEIAES
A dual band to wideband reconfigurable pentagon-shaped antenna with EBG unit cell is proposed. A minimal number of two EBG unit cell is deployed to realize frequency reconfigurable mechanism. By varying the state of the EBG the antenna is capable to change its dual band operation to wideband alternately. There are three cases that have been analysed, first case is the EBG incorporated antenna with ideal and second is with the active EBG. Subsequently, the third cases is the fabricated ideal EBG incorporated antenna. The dual band operation is at 1.8 GHz and 5.2 GHz while the wide band from 1.6 GHz to 2.37 GHz (770 MHz). The proposed reconfigurable antenna is suitable to be implemented for LTE (1.6 GHz), Wi-Fi (5.2 GHz), WiMAX (2.3 GHz) and cognitive radio application.
Towards More Reliable Renewable Power Systems - Thermal Performance Evaluatio...IJPEDS-IAES
Power electronic converters (PECs) are one of the most important elements
within renewable power generation systems. The reliability of switching
elements of PECs is still below expectations and is a major contributor to the
downtime of renewable power generation systems. Conventional technology
based elements such as Silicon Insulated Gate Bipolar Transistors (IGBTs)
operate as switching components in PECs. Recent topological improvements
have led to new devices called Silicon Carbide (SiC) MOSFETs which, are
also being used as switching elements for PECs. This paper presents detailed
investigations into the performance of those switching devices with a focus
on their reliability and thermal characteristics. Namely, trench gate NPT, FS
IGBT topologies and SiC MOSFET are firstly modelled using 3-D multiphysics
finite element modelling to gain clear understanding of their thermal
behaviour. Subsequently, modelling outcomes are verified by using those
devices as switching elements in operational boost converters. The
purposely-developed test setups are utilised to critically assess the
performances of those switching devices under different loading and
environmental conditions. In general, SiC device was found to exhibit about
20 °C less in its operating temperature and therefore expected to offer more
reliable switching element.
LINEARITY AND ANALOG PERFORMANCE ANALYSIS OF DOUBLE GATE TUNNEL FET: EFFECT O...VLSICS Design
The linearity and analog performance of a Silicon Double Gate Tunnel Field Effect Transistor (DG-TFET) is investigated and the impact of elevated temperature on the device performance degradation has been studied. The impact on the device performance due to the rise in temperature and a gate stack (GS) architecture has also been investigated for the case of Silicon DG-MOSFET and a comparison with DGTFET is made. The parameters overning the analog performance and linearity have been studied, and high frequency simulations are carried out to determine the cut-off frequency of the device and its temperature dependence.
At low frequencies, we analyze transistor
using h-parameter. But for high frequency analysis the
h-parameter model is not suitable, because :-
(1) The value of h-parameters are not constant at high frequencies.
(2)At high frequency h-parameters becomes very complex
in nature
DC performance analysis of a 20nm gate length n-type Silicon GAA junctionless...IJECEIAES
With integrated circuit scales in the 22-nm regime, conventional planar MOSFETs have approached the limit of their potential performance. To overcome short channel effects 'SCEs' that appears for deeply scaled MOSFETs beyond 10nm technology node many new device structures and channel materials have been proposed. Among these devices such as Gate-all-around FET. Recentely, junctionless GAA MOSFETs JL-GAA MOSFETs have attracted much attention since the junctionless MOSFET has been presented. In this paper, DC characteristics of an n-type JL-GAA MOSFET are presented using a 3-D quantum transport model. This new generation device is conceived with the same doping concentration level in its channel source/drain allowing to reduce fabrication complexity. The performance of our 3D JL-GAA structure with a 20nm gate length and a rectangular cross section have been obtained using SILVACO TCAD tools allowing also to study short channel effects. Our device reveals a favorable on/off current ratio and better SCE characteristics compared to an inversionmode GAA transistor. Our device reveals a threshold voltage of 0.55 V, a sub-threshold slope of 63mV / decade which approaches the ideal value, an Ion/Ioff ratio of 10e + 10 value and a drain induced barrier lowring (DIBL) value of 98mV/V.
International Journal of Computational Engineering Research (IJCER) is dedicated to protecting personal information and will make every reasonable effort to handle collected information appropriately. All information collected, as well as related requests, will be handled as carefully and efficiently as possible in accordance with IJCER standards for integrity and objectivity.
Modeling and Simulation of Biaxial Strained P-MOSFETs: Application to a Singl...IJECEIAES
The objectives of this work are focused on the application of strained silicon on MOSFET transistor. To do this, impact and benefits obtained with the use of strained silicon technology on p-channel MOSFETs are presented. This research attempt to create conventional and two-strained silicon MOSFETs fabricated from the use of TCAD, which is a simulation tool from Silvaco. In our research, two-dimensional simulation of conventional MOSFET, biaxial strained PMOSFET and dual channel strained P-MOSFET has been achieved to extract their characteristics. ATHENA and ATLAS have been used to simulate the process and validate the electronic characteristics. Our results allow showing improvements obtained by comparing the three structures and their characteristics. The maximum of carrier mobility improvement is achieved with percentage of 35.29 % and 70.59 % respectively, by result an improvement in drive current with percentage of 36.54 % and 236.71 %, and reduction of leakage current with percentage of 59.45 % and 82.75 %, the threshold voltage is also enhaced with percentage of: 60 % and 61.4%. Our simulation results highlight the importance of incorporating strain technology in MOSFET transistors.
Controlling the Radiation Pattern of Patch Antenna Using Switchable EBGTELKOMNIKA JOURNAL
The advantages of the beam steering technique are the reduction of interference, save power and to maximize connectivity for point to multi points. Antenna gain degradation is a big problem in the beam steering technique. A new antenna structure is formed by combining the concept of mushroom-like EBG structure with the switching diode to produce the radation pattern control. All sides of the patch antenna are surrounded by several cells for EBG structure. In both of the the left and right sides, through a switching pin diode, the ground plane is attached to vias. The band-stop and band-pass properties of the EBG sector can be changed with the help of switching the diode between ON and OFF state, thus yielding the beam steering into that particular sector. At 6 GHz operational frequency, this structure has the ability to steer 40º (from -20º to +20º) while minimal diodes are utilized, directivity of 10 dBi, gain 9.86 dB and the efficiency is 96.5%. This approach is robust to gain degradation and the main lobe gain is approximately constant for all steering angles.
We present this work by two steps. In the first one, the new structure proposed of the FP-HEMTs device (Field plate High Electron Mobility Transistor) with a T-gate on an 4H-SIC substrate to optimize these electrical performances, multiple field-plates were used with aluminum oxide to split the single electric field peak into several smaller peaks, and as passivation works to reduce scaling leakage current. In the next, we include a modeling of a simulation in the Tcad-Silvaco Software for realizing the study of the influence of negative voltage applied to gate T-shaped in OFF state time and high power with ambient temperature, the performance differences between the 3FP and the SFP devices are discussed in detail.
A Miniature Microstrip Antenna Array using Circular Shaped Dumbbell for ISM B...IJECEIAES
The aim of this work is the achievement, and the validation of a small microstrip patch antenna array using a circular shaped dumbbell defected ground structure. This work has been dividing into two stages: The first step is to miniaturize a microstrip patch antenna resonating at 5.8GHz, which operate in the Industrial Scientific Medical band (ISM) and the second is to use a circular defected ground structure to shift the resonance frequency of the antenna array from 5.8GHz to 2.45GHz. At last, a miniaturization up to 74.47%, relative to the original microstrip antenna array has accomplished. The antenna structure has designed, optimized and miniaturized using CST MW Studio. The obtained results have compared with Ansoft’s HFSS electromagnetic solver. The antenna array has fabricated on FR-4 substrate, and its reflection coefficient is measured.
Securing your Kubernetes cluster_ a step-by-step guide to success !KatiaHIMEUR1
Today, after several years of existence, an extremely active community and an ultra-dynamic ecosystem, Kubernetes has established itself as the de facto standard in container orchestration. Thanks to a wide range of managed services, it has never been so easy to set up a ready-to-use Kubernetes cluster.
However, this ease of use means that the subject of security in Kubernetes is often left for later, or even neglected. This exposes companies to significant risks.
In this talk, I'll show you step-by-step how to secure your Kubernetes cluster for greater peace of mind and reliability.
Elevating Tactical DDD Patterns Through Object CalisthenicsDorra BARTAGUIZ
After immersing yourself in the blue book and its red counterpart, attending DDD-focused conferences, and applying tactical patterns, you're left with a crucial question: How do I ensure my design is effective? Tactical patterns within Domain-Driven Design (DDD) serve as guiding principles for creating clear and manageable domain models. However, achieving success with these patterns requires additional guidance. Interestingly, we've observed that a set of constraints initially designed for training purposes remarkably aligns with effective pattern implementation, offering a more ‘mechanical’ approach. Let's explore together how Object Calisthenics can elevate the design of your tactical DDD patterns, offering concrete help for those venturing into DDD for the first time!
Alt. GDG Cloud Southlake #33: Boule & Rebala: Effective AppSec in SDLC using ...James Anderson
Effective Application Security in Software Delivery lifecycle using Deployment Firewall and DBOM
The modern software delivery process (or the CI/CD process) includes many tools, distributed teams, open-source code, and cloud platforms. Constant focus on speed to release software to market, along with the traditional slow and manual security checks has caused gaps in continuous security as an important piece in the software supply chain. Today organizations feel more susceptible to external and internal cyber threats due to the vast attack surface in their applications supply chain and the lack of end-to-end governance and risk management.
The software team must secure its software delivery process to avoid vulnerability and security breaches. This needs to be achieved with existing tool chains and without extensive rework of the delivery processes. This talk will present strategies and techniques for providing visibility into the true risk of the existing vulnerabilities, preventing the introduction of security issues in the software, resolving vulnerabilities in production environments quickly, and capturing the deployment bill of materials (DBOM).
Speakers:
Bob Boule
Robert Boule is a technology enthusiast with PASSION for technology and making things work along with a knack for helping others understand how things work. He comes with around 20 years of solution engineering experience in application security, software continuous delivery, and SaaS platforms. He is known for his dynamic presentations in CI/CD and application security integrated in software delivery lifecycle.
Gopinath Rebala
Gopinath Rebala is the CTO of OpsMx, where he has overall responsibility for the machine learning and data processing architectures for Secure Software Delivery. Gopi also has a strong connection with our customers, leading design and architecture for strategic implementations. Gopi is a frequent speaker and well-known leader in continuous delivery and integrating security into software delivery.
GraphRAG is All You need? LLM & Knowledge GraphGuy Korland
Guy Korland, CEO and Co-founder of FalkorDB, will review two articles on the integration of language models with knowledge graphs.
1. Unifying Large Language Models and Knowledge Graphs: A Roadmap.
https://arxiv.org/abs/2306.08302
2. Microsoft Research's GraphRAG paper and a review paper on various uses of knowledge graphs:
https://www.microsoft.com/en-us/research/blog/graphrag-unlocking-llm-discovery-on-narrative-private-data/
Smart TV Buyer Insights Survey 2024 by 91mobiles.pdf91mobiles
91mobiles recently conducted a Smart TV Buyer Insights Survey in which we asked over 3,000 respondents about the TV they own, aspects they look at on a new TV, and their TV buying preferences.
Observability Concepts EVERY Developer Should Know -- DeveloperWeek Europe.pdfPaige Cruz
Monitoring and observability aren’t traditionally found in software curriculums and many of us cobble this knowledge together from whatever vendor or ecosystem we were first introduced to and whatever is a part of your current company’s observability stack.
While the dev and ops silo continues to crumble….many organizations still relegate monitoring & observability as the purview of ops, infra and SRE teams. This is a mistake - achieving a highly observable system requires collaboration up and down the stack.
I, a former op, would like to extend an invitation to all application developers to join the observability party will share these foundational concepts to build on:
Threats to mobile devices are more prevalent and increasing in scope and complexity. Users of mobile devices desire to take full advantage of the features
available on those devices, but many of the features provide convenience and capability but sacrifice security. This best practices guide outlines steps the users can take to better protect personal devices and information.
DevOps and Testing slides at DASA ConnectKari Kakkonen
My and Rik Marselis slides at 30.5.2024 DASA Connect conference. We discuss about what is testing, then what is agile testing and finally what is Testing in DevOps. Finally we had lovely workshop with the participants trying to find out different ways to think about quality and testing in different parts of the DevOps infinity loop.
In his public lecture, Christian Timmerer provides insights into the fascinating history of video streaming, starting from its humble beginnings before YouTube to the groundbreaking technologies that now dominate platforms like Netflix and ORF ON. Timmerer also presents provocative contributions of his own that have significantly influenced the industry. He concludes by looking at future challenges and invites the audience to join in a discussion.
Pushing the limits of ePRTC: 100ns holdover for 100 daysAdtran
At WSTS 2024, Alon Stern explored the topic of parametric holdover and explained how recent research findings can be implemented in real-world PNT networks to achieve 100 nanoseconds of accuracy for up to 100 days.
Transcript: Selling digital books in 2024: Insights from industry leaders - T...BookNet Canada
The publishing industry has been selling digital audiobooks and ebooks for over a decade and has found its groove. What’s changed? What has stayed the same? Where do we go from here? Join a group of leading sales peers from across the industry for a conversation about the lessons learned since the popularization of digital books, best practices, digital book supply chain management, and more.
Link to video recording: https://bnctechforum.ca/sessions/selling-digital-books-in-2024-insights-from-industry-leaders/
Presented by BookNet Canada on May 28, 2024, with support from the Department of Canadian Heritage.
Essentials of Automations: The Art of Triggers and Actions in FMESafe Software
In this second installment of our Essentials of Automations webinar series, we’ll explore the landscape of triggers and actions, guiding you through the nuances of authoring and adapting workspaces for seamless automations. Gain an understanding of the full spectrum of triggers and actions available in FME, empowering you to enhance your workspaces for efficient automation.
We’ll kick things off by showcasing the most commonly used event-based triggers, introducing you to various automation workflows like manual triggers, schedules, directory watchers, and more. Plus, see how these elements play out in real scenarios.
Whether you’re tweaking your current setup or building from the ground up, this session will arm you with the tools and insights needed to transform your FME usage into a powerhouse of productivity. Join us to discover effective strategies that simplify complex processes, enhancing your productivity and transforming your data management practices with FME. Let’s turn complexity into clarity and make your workspaces work wonders!
The Art of the Pitch: WordPress Relationships and SalesLaura Byrne
Clients don’t know what they don’t know. What web solutions are right for them? How does WordPress come into the picture? How do you make sure you understand scope and timeline? What do you do if sometime changes?
All these questions and more will be explored as we talk about matching clients’ needs with what your agency offers without pulling teeth or pulling your hair out. Practical tips, and strategies for successful relationship building that leads to closing the deal.
State of ICS and IoT Cyber Threat Landscape Report 2024 previewPrayukth K V
The IoT and OT threat landscape report has been prepared by the Threat Research Team at Sectrio using data from Sectrio, cyber threat intelligence farming facilities spread across over 85 cities around the world. In addition, Sectrio also runs AI-based advanced threat and payload engagement facilities that serve as sinks to attract and engage sophisticated threat actors, and newer malware including new variants and latent threats that are at an earlier stage of development.
The latest edition of the OT/ICS and IoT security Threat Landscape Report 2024 also covers:
State of global ICS asset and network exposure
Sectoral targets and attacks as well as the cost of ransom
Global APT activity, AI usage, actor and tactic profiles, and implications
Rise in volumes of AI-powered cyberattacks
Major cyber events in 2024
Malware and malicious payload trends
Cyberattack types and targets
Vulnerability exploit attempts on CVEs
Attacks on counties – USA
Expansion of bot farms – how, where, and why
In-depth analysis of the cyber threat landscape across North America, South America, Europe, APAC, and the Middle East
Why are attacks on smart factories rising?
Cyber risk predictions
Axis of attacks – Europe
Systemic attacks in the Middle East
Download the full report from here:
https://sectrio.com/resources/ot-threat-landscape-reports/sectrio-releases-ot-ics-and-iot-security-threat-landscape-report-2024/
Device parameter optimization of Silicon Germanium HBT for THz applications
1. International Journal on Electrical Engineering and Informatics - Volume 2, Number 4, 2010
Device Parameter Optimization of Silicon Germanium HBT
for THz Applications
Pradeep Kumar and R. K. Chauhan
Department of ECE, M.M.M. Engineering College
Gorakhpur-273010
pradeep.hitesh@gmail.com
rkchauhan27@gmail.com
Abstract: Now-a-days SiGe HBTs are surpassing even the fastest III-V production devices
in the high–speed orbit. The state-of-art in simulation of silicon germanium semiconductor
devices is presented in this paper. A comprehensive course of action to model the device
parameter characterization of High Frequency 0.1µm SiGe HBT is depicted which is based on
the technique of direct parameter extraction. With the help of S-, Y- and Z- parameters, the
equivalent circuit parameters have been extracted in a faultless approach. The intrinsic and the
extrinsic elements of model are obtained using a direct extraction method that assists to find
out the base resistance from the Z- parameters. In this, the issues entailed in simultaneous
optimization of fmax and fT and related optimization of base resistance as well as junction
capacitance are addressed. The device characteristics of the SiGe HBT are found much
advance to those of III–V semiconductor devices. A corroboration of objective validity of the
modeling scheme and the extraction of parameter is accomplished in the form of S-parameters.
These results have been validated using a viable numerical device simulator ATLAS from
Silvaco International.
Keywords: Si, Ge grading, SiGe HBT, cut-off frequency, fmax , MSG.
1. Introduction
The silicon bipolar technologies were attaining development with delays in ECL gate
between 20 and 30 ps as well as cut-off frequency fT about 30GHz in late 80s. Further, there
were noteworthy developments when Silicon-Germanium Heterojunction bipolar transistor
(HBT) emerged from research laboratories in viable world and entered fabrication in
conventional radio frequency BiCMOS technologies in the 90s. Due to such developments, a
impressive impact on the performance on bipolar transistors was noticed which in turn caused
fT values approaching 400GHz and values of ECL gate delays less than 5 ps. In addition, SiGe
BiCMOS technology is sincerely challenging III/V and II/VI technologies in realm of high-
frequency electronics applications, for example optical fibre and mobile communications.
Also, the way for employing SiGe in CMOS technologies have been cemented by these
successes of SiGe in bipolar technologies.
Since SiGe is used to furnish improved channel mobility in a number of different types of
Heterojunction MOSFET, an akin revolution is now in progress in the fabrication of MOS
transistors. 0.13 mm CMOS device technology in present is soundly compatible with the
devices. The viability of consciousness of a complete wireless system on-a-chip is presented by
this compatibility. The emergence of Silicon Germanium BiCMOS technology by combining
Si1-xGex HBT circuits with digital application-specific integrated circuits (ASICs) is currently
in highly production. From Ammar & R.K.Chauhan model, it is suggested that the current gain
of the SiGe HBT can be tailored effectively for high speed applications and it is also inferred
that such HBTs have greater flexibility in the design compared to BJTs as one can easily
reduce the base resistance without losing much of the gain [1]. Upcoming generation of 40, 80,
Received: August 13, 2010. Accepted: December 27, 2010 343
Electronic copy available at: http://ssrn.com/abstract=2118519
2. Pradeep Kumar, et al.
or 100 Gb/s communications channels will be operated, due to complete improvement of
optical-fiber trunk lines in comparison with the current 2.5-10 Gb/s communications channels.
It is estimated that manufacture of 100 Gb/s links might be pace since 2010-2011.
In this paper, we explored the upshot of Ge grading on the performance of Si1-xGex HBT.
The extrapolated maximum oscillation-frequency fmax , cutoff frequency fT, stability, Figure-of
merit, power gain and various intrinsic as well as extrinsic parameters are calculated for
different Ge concentrations with linear grading. Following this motivation, in second section,
we address model of Si1-xGex HBT and its elements. In Section-III, we discuss the high
frequency characterization. In the fourth Section, we address the HF modeling and
performance factors of this SiGe HBT with the help of small-signal analysis as well as in fifth
section, we discuss the results based on ATLAS. Finally, in section sixth, we concluded with
common projections and observations.
2. Model
The energy-band diagram of resultant device is the paramount mean to portray a range of
consequences of introducing Ge into the base region of SiGe HBT by comparing it to Si. The
graded base induces a drift field across the neutral base that is aligned in a direction (from
collector to emitter). This causes an acceleration of induced minority electrons across the base.
Consequently, this large drift field component is a domino effect for electron transport
phenomenon. Hence, by effectively speeding up the diffusive transport of the minority carriers
a decrement in the base transit time occurs. Although the band offsets in SiGe HBTs are
usually small in comparison to the band offsets of III-V technology standards, the large electric
fields are translated by the Ge grading over the short distance of neutral base and this electric
field is ample to speed up the electrons to near saturation velocity. In comparison to SiGe HBT,
the base transit time typically limits the frequency response of the Si BJT. Therefore it could be
predictable that the frequency response should be improved appreciably by the Ge- induced
drift field [2]. The cross-section of the SiGe HBT base is shown in Figure (1.b).The bandgap of
SiGe HBT is given by [3],
SiGe = Si Ge
Eg E g . (1 − x) + E g . x + C g . (1 − x) . x (1)
Where x is Ge conc. and Cg = -0.4 eV is a bowing parameter. Ge is compositionally graded
from the emitter-base (EB) junction with lower concentration to the collector–base (CB)
junction with higher concentration and it is shown as dashed line in Figure (1.a). Due to this
impact, the SiGe HBT consists of a finite band offset at the EB junction and a larger band
offset at the CB junction. Bandgap grading is easily used for position dependence of the band
offset with respect to Si. An electric field is produced by such position dependence in the Ge
induced band offset in the neutral base region. This effect aids the transportation of minority
carriers (electrons) from emitter to collector, which in turn improve the frequency response [4-
6], [7-1].
Thus we can say apparently from Figure (1.a) that the Ge-induced reduction in base
bandgap takes place at the EB edge of the quasi-neutral base ΔEg,Ge (x=0) along with the CB
edge of the quasi-neutral base ΔEg,Ge (x=Wb). Thus the graded bandgap is given by equation as
[8],
ΔE g.Ge ( grade) = ΔE (Wb ) − ΔE g .Ge (0) (2)
g.Ge
Such Ge grading across the neutral base induces a built-in-quasi drift field ξ.
344
Electronic copy available at: http://ssrn.com/abstract=2118519
3. Device Parameter Optimization of Silicon Germanium HBT
Figure 1a. Energy band diagram for a Si
BJT and graded-base SiGe HBT, both Figure 1b. The cross-section of Sige HBT
biased in forward active mode at low
injection
For instance, compared to a comparably designed Si BJT, the Ge-induced band offsets in a
SiGe HBT exponetially counteracts the the bandgap narrowing of the emitter to produce a
current-gain as [2],
ΔE g .Ge( grade)
ΔE g .Ge(0) / kT
β SiGe kTe
= γη (3)
β Si − ΔE g .Ge( grade) / kT
1− e
The base transit time of SiGe HBT is compared to the base transit time of Si transistor as [8],
τ B, SiGe ⎧ ⎡ − ΔE g , Ge( grade) ⎤⎫
2 kT ⎪ kT ⎪
= . . ⎨1 − ⎢1 − e / kT ⎥ ⎬
τ B, Si η ΔE g , Ge( grade) ⎪ ΔE g , Ge ( grade) ⎢ ⎥⎪
⎩ ⎣ ⎦⎭
(4)
And η is the electron diffusivity ratio between SiGe and Si as [8],
( Dnb ) SiGe
η = (5)
( Dnb ) Si
And an “effective density-of-states ratio” between SiGe and Si according to
( N c N v ) SiGe
γ = < 1 (6)
( N c N v ) Si
345
4. Pradeep Kumar, et al.
Thus built-in field increases on decreasing the base width so the transit time decreases on
higher built-in field ξ and higher collector current Ic. Here WB is the width of the quasi-neutral
base; Dnb is the diffusion coefficient of the minority- carrier electrons in the base. The cut-off
frequency fT can be calculated from the following expression of the Total emitter-collector
delay time as [11],
η kT
12 π f = τ B + τ c + ( C BE + C BC ) + ( R E + Rc ) C BC (7)
T qI c
It is understandable that the cut-off frequency inversely depend on the base transit time τB.
So higher cut-off frequency devices need the smaller value of the transit time. The maximum
oscillation frequency fmax is calculated from fT as [2],
fT
f max = (8)
8π C CB R B
Where CBC is the base-collector junction capacitance and RB is the base resistance. Thus
from equation (8) it is comprehensible that lower base-collector junction capacitance and base
resistance are required for the higher value of fmax . So the cut-off frequency fT is increases as
transit time decreases which in turn affect the fmax [3-8].
3. High Frequency (THz) Characterization
High frequency devices are characterized by several methods. These methods include the
scattering parameter(S-parameter) measurement by means of a network analyzer. S-parameter
measurement is a mean of a small signal measurement. The main issue in this measurement is
the calibration with accurately de-embedding the parasitic. The load-pull measurement, a very
useful technique is used for power measurements, even though it is costly and time consuming.
A set of two-port parameters [including Z-, Y-, H-, ABCD-, and S- parameters] are used to
describe the small signal RF performance of SiGe HBT. One type of parameters can simply be
converted into another type of parameters with the help of matrix manipulation. The Y-
parameters are frequently most suitable for equivalent circuit based analysis whereas the s-
parameters are almost absolutely used for RF as well as microwave measurements due to
practical reasons [12].
A. S-parameters:
The device under test (DUT) often oscillates by open and short terminations because at
very high frequencies, accurate open and short circuits are not easy to attain due to inherent
parasitic capacitances and inductances. The interconnection between the DUT and test
apparatus is also akin to the wavelength. The consideration of distributive effects is required in
this case. So S-parameters were developed and are almost absolutely used to portray transistor
RF with Microwave performance due to these practical difficulties.
S-parameters have almost similar information like Z-, Y-, or H-parameters. But the
difference between them is that the dependent and independent variables are no longer simple
voltages and the currents in S-parameters. In addition, in the s-parameter four “voltage waves”
are produced by linear combinations of the simple variables. These voltage waves hold the
identical information because they are chosen to be linearly independent. Transmission line
techniques are used to compute s-parameters at high frequencies by properly selection of these
combinations.
If incident wave is indicated by ‘a’ and reflection or scattering is indicated by ‘b’. Here the
voltage waves are defined using voltages and currents for characteristic impedance Z0. Thus
346
5. Device Parameter Optimization of Silicon Germanium HBT
voltages (a1, a2) are called incident waves, while (b1, b2) are called scattered waves. A set of
linear equations is used to relate the scattered waves with the incident waves by just as the port
voltages are related to the port currents by Z-parameters.
It is expressed like,
⎛ b1 ⎞ ⎛ S11 S12 ⎞ ⎛ a1 ⎞
⎜ ⎟=⎜ ⎟⎜ ⎟ (9)
⎜b ⎟ ⎜S S ⎟⎜a ⎟
⎝ 2 ⎠ ⎝ 21 22 ⎠ ⎝ 2 ⎠
Where,
S11 is simply reflection coefficient corresponding to input impedance with Z0 output
termination
S22 is output reflection coefficient looking back into the output for Z0 source termination.
S 21 2 is transducer gain for a Z0 source and Z0 load.
2
S12 is reverse transducer gain for a Z0 source and a Z0 load. Thus S-parameters of a
SiGe HBT will thoroughly depend on the size of transistor, frequency of operation as well
as on biasing condition.
B. De-Embedding:
De-Embedding is the process for removing; de-embed (the surrounding parasitic). This is
done for characterizing only intrinsic part of the device. There are numerous ways to de-embed
the parasitic with diverse levels of precision and complication. The first simple and directly
way is to apply lumped circuit model for representing the parasitic. Secondly, compose device
under test with different width by using identical metal pattern. When it is done then
admittance is used to estimate the parasitic. This admittance is achieved when the width is
extrapolated to zero. Furthermore, relate the similar calibrations routines and these routines are
built-in VNA. Thus De-Embedding process can be completed by two ways; initially by using
the calibration structures during calibrating the network analyzer and secondly by calibration
on standard ISS (impedance standard substrate).
4. HF Modeling and Performance Factors
In this section we develop a novel and uncomplicated extraction method for discussing the
transistor RF performance along with procedures to find out the parameters of SiGe HBT by
means of small-signal Π topology equivalent circuits of this HBT. The algorithm is helpful for
extracting both intrinsic plus extrinsic (parasitic) elements. If we determine formerly the
extrinsic elements of the HBT then conventional procedures or methods derived from simple
bias measurements work very sound. Through different procedures for example DC, cut-off
measurements, or optimization can be used for this approach. Since the typical DC and cut-off
techniques present poor performance for Silicon Germanium HBT devices that’s why it is
frequently very hard to precisely determine the values of parasitic elements of the HBT. An
innovative technique has been developed to circumvent this problem and in this technique only
scattering (S)-parameters at different biases are measured. For fitting the measured S-
parameters appropriately, linear models by way of a Π topology have been experienced. We
have neglected emitter resistance, the collector resistance, along with the output resistance due
to Early effect for simplicity [13].
S-parameters obtained from ac analysis are simply converted into Y-, Z- or H-parameters
using ATLAS. Various Power Gains for example MAG (maximum available gain), MSG
(maximum stable gain) as well as MAUG (maximum available unilateral gain) are used for
analysis. Furthermore, a Figure-of-merit that has been used extensively for microwave
347
6. Pradeep Kumar, et al.
characterization is MSG. Due to simplicity of measurement at high frequencies these quantities
are calculated from the measured small-signal scattering parameters.
The maximum stable gain is calculated by y21 and y12 as,
y 21
MSG = (10)
y12
And the maximum available gain is extracted as,
y 21 ⎛ ⎞
MAG = ⎜ k − k 2 − 1 ⎟ (11)
y12 ⎜⎝
⎟
⎠
INTRINSIC HBT
Rbc
B’ C’
Cbc
+
Vi
Cbe Rbe In Rce Cce
-
(b)
E’
Figure 2 A small-signal Π equivalent circuit of an HBT device (a) contains intrinsic and
extrinsic circuit elements. The intrinsic elements (b) can be determined from the admittance
parameters of the device at a number of different bias points.
Where k is ‘Rollett stability factor’ and extracted by this equation as,
2 Re ( y11 ) Re ( y 22 ) − Re( y12 y 21 )
k= (12)
y12 y 21
348
7. Device Parameter Optimization of Silicon Germanium HBT
Mansion’s gain is obtained by the following equation as,
2
y 21 − y 21
U= (13)
4[Re( y11 ) Re( y 22 ) − Re( y12 ) Re( y 21 )]
The maximum available unilateral gain is calculated by this equation as,
2
y 21
MAUG = (14)
4 Re( y11 ) Re( y 22 )
When both input and output are concurrently conjugate matched, at this state we achieve
MAG. When k > 1, at this the device is unconditionally stable and MAG exists. It is obvious
from equations (13) and (14), if the device is unilateral (y12 = 0) then U equals to MAUG.
When the device is unconditionally stable then MAG equals to MSG and vice-versa. Maximum
frequency at which MSG becomes unity is frequently termed as fmax. As power gain with no
impedance transformation is achieved by common-emitter microwave transistors. This is the
reason why these transistors may comprise useful gain when inserted into a system with 50 Ω.
For this model, MSG (maximum stable gain) is called FOM (Figure of merit). This device
is unconditionally stable here.
fT does not consider the limitations due to physical base resistance RB but it is usually used
to depict the frequency response of a bipolar transistor. Moreover another parameter named
maximum oscillation frequency fmax includes the effect of RB, with the parameters in fT . The
maximum oscillation frequency fmax is the extrapolated frequency at which the small signal
power gain is reduced to unity when the terminations are conjugatly matched at both input and
output. From the extrapolation of the high-frequency asymptote of a plot of the magnitude of
h21 in dB versus log (frequency), we can extract the unity gain cut-off frequency. At amply low
frequency most bipolar transistor devices may be depicted as single pole devices. This theory is
alike to a high-frequency asymptote with a slope of −20 dB per decade so is the cut-off
frequency though both CBE and CBC capacitances are bias dependent. fmax is extracted at the
point where MSG becomes 0 dB from MSG (in dB) versus log (frequency) plot [14-15].
We can achieve the intrinsic elements from the admittance parameters of the HBT device
for each bias point after a usual de-embedding process for taking the consequence of parasitic
elements. The intrinsic elements for example CBE (base-emitter capacitance) vary with
frequency. The intrinsic part of the device (Figure 2b) is contained by the given circuit
topology of the small-signal model which is shown by dashed box in Figure (2a). For a number
of different devices tested, the estimated values of the pad parasitic capacitances Cpbi along
with Cpci do not surpass hundredths of femto Farads (fF) due to this fact these capacitances can
be omitted. The intrinsic and extrinsic parameters in Figure 2 can be extracted by the following
method [16]:
The base-emitter junction capacitance is calculated by the equation as follow [16],
I m [ y11 ] + I m [ y12 ]
C BE = (15)
ωi
The base-collector junction capacitance is expressed by the equation as follow [16],
− I m [ y12 ]
C BC = (16)
ωi
349
8. Pradeep Kumar, et al.
The base-collector junction capacitance is expressed by the equation as follow [16],
I [ y ] + I m [ y12 ]
C CE = m 22 (17)
ωi
The base-collector junction capacitance is calculated by the equation as follow [16],
−1
R BC = (18)
Re[Y12 ]
The collector-emitter junction resistance is obtained by the equation as follow [16],
1
RCE = (19)
Re[Y12 ] + Re[Y22 ]
The collector-emitter junction resistance is expressed by the equation as follow [16],
1
R BE = (20)
Re[Y11 ] + Re[Y12 ]
And extrinsic resistance is obtained by the equation as follow [16],
R EXTRINSIC = Z 11 − Z 12 (21)
In this method CBE are intrinsic junction capacitances and RBC, RCE and RBE are intrinsic
junction resistances.
5. Results and Discussion
Based on the above model the values of fmax / fT and various intrinsic as well as extrinsic
elements are calculated for n-p-n SiGe HBT at different Ge concentrations for linearly graded
Ge. For this purpose ATLAS from SILVACO International is used. The HBT considered in
this paper has the base width of 0.1µm. Average Ge concentration in this base region
considered in our calculations is varied from 8%-25% as higher to this are not supported by
present epitaxial technologies and beyond it the improvement associated with Ge seizes may be
due to lattice constant mismatch as in Figure 6. ATLAS simulation of SiGe HBT is performed
to prove precision.
With the intention of getting excellent accord with measured characteristics, all the
important physical effects, for example impact ionization (II) is appropriately modeled and
accounted for the simulation as well. The impact ionization leads to a strong enhancement of
Ic. AC simulation needs apposite DC calibration which is an important prerequisite for it. For
this simulation, it is compulsory to take the complete device composition into account with the
aim of considering the capacitance between substrate and collector (CCS) as well as capacitance
between base and collector (CBC). Figure 3.1 to Figure 3.3 show the simulated S-parameters at
VCE = 1V for this device. Because of the intuitive relationship between coefficients S11 and S22
are conveniently on a smith chart, while S21 and S12 are representing the gain response that’s
why they are typically displayed on a polar plot. The methods other than the method of polar
plot are not convenient to represent the gain like Figure 7 ‘mod of S12 (dB) and mod of S21 (dB)
vs. frequency plot’ (bode plot). In the Figure 3.1 to 3.3, the S11 for a bipolar transistor always
moves clockwise as frequency increases on the smith chart. The S11 data at higher IC in general
shows a smaller negative reactance, because of the higher EB diffusion capacitance.
350
9. Device Parameter Optimization of Silicon Germanium HBT
Figure 3.1. Simulated S11 and S22 Figure 3.2. Simulated S21 parameter Figure 3.3. Simulated S12 parameter
The S21 magnitude Parameter from ATLAS Parameter from ATLAS
Parameters from ATLAS decreases with increasing frequency, as expected, because of decreasing
at 0.25 Ge concentrations while S atis larger at higher I because ofat 0.25 Ge concentrations bias
forward transducer gain, 0.25 Ge concentrations the higher f at that
21 C T
current. It follows from the above discussion that the S-parameters of a SiGe HBT will
intimately depend on the transistor size, biasing condition and operating frequency [17]. Using
ATLAS and above HF model the extrapolated fmax is calculated 16.8 THz and fT is calculated
13.5 THz for 0.25 Ge concentration. Figure 5 shows the power gain MSG (dB) vs. frequency
(Hz). At 8.19 GHz frequency Figure-of-merit MSG at 0.25 Ge concentration is calculated
31.54 dB.
351
10. Pradeep Kumar, et al.
Figure 4. Gummel plot of SiGe HBT as a function of EB voltage for an SiGe HBT
Figure 5. MSG (dB) vs. frequency (Hz) plot at 0.25 Ge conc.
The Gummel plot for this model at 1V forward bias is plotted in Figure 4. The plot in
Figure 4 shows the variation of collector current and base current w.r.t. bias voltage. This plot
indicates to the important dc consequence of adding Ge into the base, however, lies with the
collector current density [2]. Physically, the barrier to electron injection at the EB junction is
reduced by introducing Ge into the base, yielding more charge transport from emitter-to-
collector for a given applied EB bias. Observe from Figure (1.a) that in this linearly graded-
base design, the emitter region of the SiGe HBT and Si BJT comparison are essentially
identical, implying that the resultant base current density of the two transistors will be roughly
the same. The net result is that the introduction of Ge increases the current gain of the transistor
(β=collector current density / base current density). From a more device–physics oriented
viewpoint, the Ge-induced band offset exponentially decreases the intrinsic carrier density in
the base which, in turn, decreases the base Gummel number and, hence, increases collector
current density. Meaningful in this context is the Ge-induced improvement in β over a
comparably constructed Si BJT [2].
The intrinsic and the extrinsic parameters are calculated for the above model of SiGe HBT.
The values of these parameters are in the Table.1.
Table.1 Summary of Device parameters from2D simulation
Ge conc. fmax (THz) RB(Ω.μm) CBC(f F) CBE(f F) CCE(f F)
0.2 8.39 5.71 72 44.33 54.7
0.25 16.8 4.251 66 27.9 52.45
Ge concentration vs fmax (THz)
18
16
14
12
fmax
10
8
6
4
2
0
0 0.05 0.1 0.15 0.2 0.25 0.3
Ge concentration
352
11. Device Parameter Optimization of Silicon Germanium HBT
Figure 6. Plot of fmax (THz) vs. Ge concentration
Now we will discuss some practical issues of employing the base region optimization
approach. This device results in the lower power consumption which can be used for battery
operated low cost devices for high speed applications. Now-a-days research shows that
applications in high-frequency communications and radar employ the wide bandwidth
heterojunction bipolar transistors (HBTs). ICs for 40 Gb/s transmission are currently in
development in optical fiber communications. Ample improvements in the bandwidth of
semiconductor electronics indicate that this improved bandwidth will be utilized by the
emerging 160 Gb/s transmission equipment in the vicinity of future. Thus it can be proposed
that devices with THz frequency are used for dust and line as well as continuant radiation from
cool (5-100 K) gas (molecules and atoms).
This HBT in Tera-Hertz frequencies encompass definite water absorption rates and imitate
off metal, except this it can usually infiltrate fog and fabrics [18]. Chemical detection,
medicine, chemical spectroscopy, transportation and national security in addition with weapon
fields will also be enriched with this HBT. The study of Dust & gas chemistry, stellar and
galactic constituents as well as evolution cosmology will be helped by these THz devices. This
HBT in THz Radar will accommodate in investigating hidden universe and planet.
Figure 7. Mod S12(dB) and mod S21(dB) vs. Frequency plot (Hz)
Conclusion
In this paper, a detailed investigation has been made to study the impact of Ge content and
Ge grading in the SiGe-HBT base on the performance of the HBT. An electric field is
produced by position dependence in the Ge induced band offset in the neutral base region. This
effect aids the transportation of minority carriers (electrons) from emitter to collector, which in
turn improve the frequency response. High frequency devices are characterized by extracted s-
parameters. S-parameters are measured by means of a small signal measurement. In this paper,
we develop a novel and uncomplicated extraction method for discussing the transistor RF
performance along with procedures to find out the parameters of SiGe HBT by means of small-
signal Π topology equivalent circuits of this HBT. S-parameters obtained from ac analysis are
353
12. Pradeep Kumar, et al.
simply converted into Y-, Z- or H-parameters using ATLAS. Further the intrinsic and extrinsic
parameters which affect the fmax/fT are calculated. The base-region optimizations can effectively
improve the power-gain values of Si1-xGex HBTs in a wide frequency range. In this model, the
power gain MSG produces the THz fmax/fT which is very fruitful for the tera Hz applications.
The extrapolated fmax using ATLAS is calculated 16.8 THz and fT are calculated 13.5 THz for
0.25 Ge concentration. At 8.19 GHz frequency MSG at 0.25 Ge concentration is calculated
31.54 dB. Low base resistance for SiGe power HBTs are realized by the appositely optimized
base-region with a high Ge content of appropriate form. This model is also used to realize
microwave power amplification at high frequencies using these devices has been verified to be
viable.
References
[1] Vishal, Ammar and R.K. Chauhan. “Performance Analysis of a Bandgap Engineered
Silicon Bipolar Transistor”, Proc of International Conference “ELECTRO-2009”, IT
BHU, Dec. 22-24, (2009).
[2] J. D. Cressler. SiGe HBT technology: “a new contender for Si-based RF and microwave
circuit applications”. IEEE Trans. Microw. Theory Tech., vol. 46, issue 5, 572 (1998).
[3] V. Palankovski and S. Selberherr. “Critical modeling issues of SiGe semiconductor
devices”, J. Telecommun. Inform. Technol., no. 1, 15 (2004).
[4] Ankit Kashyap and R. K. Chauhan. “Profile Design optimization of SiGe based HBT for
High Speed Applications”, Journal of Computational and Theoretical Nanosciences,
Vol. 5, 2238, (2008).
[5] Ankit Kashyap and R. K. Chauhan. “Effect of the Ge profile design on the performance
of an n-p-n SiGe HBT-based analog circuit”, Microelectronics journal, MEJ: 2554,
(2008).
[6] Mukul K Das, N. R. Das and P. K. Basu. “Performance Analysis of a SiGe/Si
Heterojunction Bipolar Transistor for Different Ge-composition”, Proc. of the
International Conf. URSI-GA, New Delhi, D03.7 (2005).
[7] Ankit Kashyap, Ashok Kumar and R. K. Chauhan. “Design of a High Speed SiGe HBT
for Wireless Applications”, Proc. of International Conference IICT-2007, DIT,
Dehradoon July 27-28 (2007).
[8] John D. Cressler. “Emerging SiGe HBT Reliability Issues for Mixed-Signal Circuit
Applications”, IEEE Transactions on Device and Materials Reliability, vol. 4, no. 2
(2004).
[9] Richard S. Muller, Kamins and Mansun Chan. “Device Electronics for Integrated
Circuits”, 3rd ed., Jhon Wiley & Sons Publication (2002).
[10] Peter Ashburn. “SiGe Hetrojunction Bipolar Transistors”, Jhon Wiley & Sons Publication
(2003).
[11] Ping-Chun Yeh, Chih-Hung Hsieh, Chwan-Ying Lee, Yu-Lin Chu, Kuan-Lun Chang,
Denny Tang , John Chern and Hwann-Kaeo Chiou. “Geometrical Effect Analysis on fT
and fmax of 0.18 μm SiGe HBT”, Microwave and RF Laboratory, PAWorkshop, National
Central University (2004).
[12] Lars Vestling. “Design and Modeling of High-Frequency LDMOS Transistors”, 681,
ACTA. Universitatis UPSALIENSIS UPPSALA (2002).
[13] ATLAS User’s Manual DEVICE SIMULATION SOFTWARE, SILVACO International,
(2004).
[14] Zhenqiang Ma, Saeed Mohammadi, Pallab Bhattacharya, Linda P. B. Katehi, Samuel A.
Alterovitz, George E. Ponchak. “A High-Power and High-Gain X-Band Si/SiGe/Si
Heterojunction Bipolar Transistor”, IEEE Transactions on Microwave Theory and
Techniques, vol. 50, No. 4, April (2002).
354
13. Device Parameter Optimization of Silicon Germanium HBT
[15] Zhenqiang Ma and Ningyue Jiang. “Base–Region Optimization of SiGe HBTs for High-
Frequency Microwave Power Amplification”, IEEE Transactions on Electron Devices,
vol. 53, No.4, April (2006).
[16] J. M. Zamanillo, A. Tazon, A. Mediavilla and C. Navarro. “Simple Algorithm Extracts
SiGe HBT Parameters”, MICROWAVES & RF (1999).
[17] Application note 154 on S-Parameter Design, Hewlett-Packard (1990).
[18] Frank Chang. ”Terahertz CMOS SoC for Imaging/Communication Systems”, UCLA,
High-Speed Electronics Laboratory.
Pradeep Kumar was born in Allahabad, India in 1985. He received his
B.Tech. degree in Electronics & Communication Engineering in 2006. He
initially joined VINCENTIT Hyderabad in 2006 and thereafter worked as a
lecturer in Dr. K.N.M.I.E.T. Modinagar, Ghaziabad between 2007 and 2008.
He is currently pursuing the M.Tech. degree in Digital Systems from Madan
Mohan Malviya Engineering College, Gorakhpur, India. His M.Tech. thesis
is dedicated towards the modeling and device parameter optimization of
Silicon-Germanium HBT for THz applications.
e-mail: pradeep.hitesh@gmail.com
Ph: +91-9453291241
Deparment of ECE, Madan Mohan Malviya Engineering College, Gorakhpur-273010, India.
R. K. Chauhan was born in Dehradoon, India in 1967. He received the
B.Tech. degree in Electronics & Communication Engineering, from
G.B.P.U.A.T - Pantnagar, in 1989 and M.E. in Control & Instrumentation,
from MNNIT-Allahabad in 1993 and Ph.D in Electronics Engineering, from
IT-BHU, Varanasi, INDIA in 2002. He joined the department of ECE, Madan
Mohan Malviya Engineering College, Gorakhpur, India as a lecturer, in 1993,
as an Assistant Professor since 2002 and thereafter as an Associate Professor
since Jan, 2006 to till date in the same institute. He also worked as a
Professor in Department of ECE, Faculty of Technology, Addis Ababa University, Ethiopia
between 2003 to 2005. He is reviewer of Microelectronics Journal, CSP etc.. His research
interests include device modeling and simulation of MOS, CMOS and HBT based circuits. He
was selected as one of top 100 Engineers of 2010 by International Biographical Centre,
Cambridge, England.
e-mail: rkchauhan27@gmail.com
Ph: +91-9235500556
Department of ECE, Madan Mohan Malviya Engineering College, Gorakhpur-273010, India.
355