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Author: Jinwook Will Chung
Publisher:
ISBN:
Category :
Languages : en
Pages : 160
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Book Description
In this thesis, we have used a combination of physical analysis, numerical simulation and experimental work to identify and overcome some of the main challenges in AlGaN/GaN high electron mobility transistors (HEMTs) for high frequency applications. In spite of their excellent material properties, GaN-based HEMTs are still below the theoretical predictions in their high frequency performance. If the frequency performance could be improved, the superior breakdown characteristics of nitride semiconductors would make these devices the best option for power amplifiers at any frequency. To achieve this goal, we have first identified some critical parameters that limit the high frequency performance of AlGaN/GaN HEMTs and then we have demonstrated several new technologies to increase the performance. Some of these technologies include advanced drain delay engineering, charge control in the channel and new N-face GaN HEMTs. Although more work is needed in the future to combine all these new technologies, the initial results are extremely promising.
Author: Jinwook Will Chung
Publisher:
ISBN:
Category :
Languages : en
Pages : 160
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Book Description
In this thesis, we have used a combination of physical analysis, numerical simulation and experimental work to identify and overcome some of the main challenges in AlGaN/GaN high electron mobility transistors (HEMTs) for high frequency applications. In spite of their excellent material properties, GaN-based HEMTs are still below the theoretical predictions in their high frequency performance. If the frequency performance could be improved, the superior breakdown characteristics of nitride semiconductors would make these devices the best option for power amplifiers at any frequency. To achieve this goal, we have first identified some critical parameters that limit the high frequency performance of AlGaN/GaN HEMTs and then we have demonstrated several new technologies to increase the performance. Some of these technologies include advanced drain delay engineering, charge control in the channel and new N-face GaN HEMTs. Although more work is needed in the future to combine all these new technologies, the initial results are extremely promising.
Author: Jinwook Will Chung
Publisher:
ISBN:
Category :
Languages : en
Pages : 183
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Book Description
In spite of the great progress in performance achieved during the last few years, GaN high electron mobility transistors (HEMTs) still have several important issues to be solved for millimeter-wave (30 ~ 300 GHz) applications. One of the key challenges is to improve its high frequency characteristics. In this thesis, we particularly focus on fT and fma, two of the most important figures of merit in frequency performance of GaN HEMTs and investigate them both analytically and experimentally. Based on an improved physical understanding and new process technologies, we aim to demonstrate the state-of-the-art high frequency performance of GaN HEMTs. To maximize fmax, parasitic components in the device (Ri, R, Rg, Cgd, and go) are carefully minimized and the optimized 60-nm AlGaN/GaN HEMT shows a very high fmax of 300 GHz. The lower-than-expected fT observed in many AlGaN/GaN HEMTs is attributed to a significant drop of the intrinsic transconductance at high frequency (RF gm) with respect to the intrinsic DC g. (called RF gm-collapse). By suppressing RF gm-collapse and harmoniously scaling the device, a record fT of 225 GHz is achieved in the 55-nm AlGaN/GaN HEMT. Another important challenge for the wide adoption of GaN devices is to develop suitable technology to integrate these GaN transistors with Si(100) electronics. In this thesis, we demonstrate a new technology to integrate, for the first time, GaN HEMTs and Si(100) MOSFETs on the same chip. This integration enables the development of hybrid circuits that take advantage of the high-frequency and power capability of GaN and the unsurpassed circuit scalability and complexity of Si electronics.
Author: Jutta Kühn
Publisher: KIT Scientific Publishing
ISBN: 3866446152
Category : Power amplifiers
Languages : en
Pages : 264
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Book Description
This work has arisen out of the strong demand for a superior power-added efficiency (PAE) of AlGaN/GaN high electron mobility transistor (HEMT) high-power amplifiers (HPAs) that are part of any advanced wireless multifunctional RF-system with limited prime energy. Different concepts and approaches on device and design level for PAE improvements are analyzed, e.g. structural and layout changes of the GaN transistor and advanced circuit design techniques for PAE improvements of GaN HEMT HPAs.
Author: Pil Sung Park
Publisher:
ISBN:
Category :
Languages : en
Pages : 159
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Book Description
Abstract: In this thesis, we have investigated and overcome the major limiting factors of intrinsic and parasitic parameters in III-Nitride high electron mobility transistors for high frequency performance with a combined study of simulations and experimental work. The high frequency RF performance of these transistors is severely degraded when short-channel effects, and parasitic resistances are present. To investigate short-channel effects, first, we have developed a simulation model for Ga-polar and N-polar HEMT structures, and found the main reasons for these degradations are drain-induced barrier-lowering and space-charge-limited current injection. To mitigate this, a strong electrostatic back-barrier structure from N-polar orientation is suggested. Secondly, the effect of quantum displacement in GaN HEMTs were investigated using both simulation and experimental measurements. It was discovered that the quantum displacement in a highly scaled device can give more than 2x change in the gate-source capacitance between two different orientations. Therefore it is imperative that the device design for such highly scaled devices consider quantum displacement effects in order to avoid short-channel effects. Another limiting factor from extrinsic elements is the parasitic resistances, especially from contact resistance. To achieve low-resistance non-alloyed Ohmic contacts, we developed two new process technologies that included an inserted graphene layer between metal and AlGaN, and a graded n+ AlGaN Ohmic layer. Both approaches utilized the current path where no barrier exists. In this work, we set the record low contact resistance of 0.049 Ohm mm for Ga-polar technology using the graded AlGaN scheme. The most crucial factor for improving high frequency performance for III-Nitride HEMTs is the saturation of the effective electron velocity. We have modeled the velocity saturation in GaN channel based on LO phonon emission, and explain the phenomena of rapidly decreasing behavior transconductance. This model was also applied to 2-D device simulation where it was possible to obtain the DC and RF characteristics matching to the experimental results. To overcome the fast reduction in gm and fT, we have introduced a polarization graded channel in AlGaN/GaN HEMT and graded AlGaN HFET to tailor the charge profile, and demonstrated a flat gm profile for the first time in field-effect-transistor structure. The high frequency performance of this engineered channel was measured from a highly scaled graded AlGaN HFET with advanced process technology including contact layer regrowth and e-beam lithography. Although the flat gm improved the linearity of fT and fmax, they do not stay flat due to an increasing capacitance profile in a regular 2 X 50 micrometre device. With further scaling of the device width, we obtained an increasing gm profile which can compensate the increment of capacitance, and finally we demonstrated flat fT and fmax profile which has been unseen in any field-effect-transistors. All these results shown in this thesis can contribute to further improvements in high frequency and high power performance of III-Nitride HEMTs for the future RF application beyond mm-Wave frequency.
Author: Gaudenzio Meneghesso
Publisher: Springer
ISBN: 331977994X
Category : Technology & Engineering
Languages : en
Pages : 242
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Book Description
This book demonstrates to readers why Gallium Nitride (GaN) transistors have a superior performance as compared to the already mature Silicon technology. The new GaN-based transistors here described enable both high frequency and high efficiency power conversion, leading to smaller and more efficient power systems. Coverage includes i) GaN substrates and device physics; ii) innovative GaN -transistors structure (lateral and vertical); iii) reliability and robustness of GaN-power transistors; iv) impact of parasitic on GaN based power conversion, v) new power converter architectures and vi) GaN in switched mode power conversion. Provides single-source reference to Gallium Nitride (GaN)-based technologies, from the material level to circuit level, both for power conversions architectures and switched mode power amplifiers; Demonstrates how GaN is a superior technology for switching devices, enabling both high frequency, high efficiency and lower cost power conversion; Enables design of smaller, cheaper and more efficient power supplies.
Author: D. Nirmal
Publisher: CRC Press
ISBN: 0429862520
Category : Science
Languages : en
Pages : 434
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Book Description
This book focusses on III-V high electron mobility transistors (HEMTs) including basic physics, material used, fabrications details, modeling, simulation, and other important aspects. It initiates by describing principle of operation, material systems and material technologies followed by description of the structure, I-V characteristics, modeling of DC and RF parameters of AlGaN/GaN HEMTs. The book also provides information about source/drain engineering, gate engineering and channel engineering techniques used to improve the DC-RF and breakdown performance of HEMTs. Finally, the book also highlights the importance of metal oxide semiconductor high electron mobility transistors (MOS-HEMT). Key Features Combines III-As/P/N HEMTs with reliability and current status in single volume Includes AC/DC modelling and (sub)millimeter wave devices with reliability analysis Covers all theoretical and experimental aspects of HEMTs Discusses AlGaN/GaN transistors Presents DC, RF and breakdown characteristics of HEMTs on various material systems using graphs and plots
Author: Sazia Afreen Eliza
Publisher:
ISBN:
Category :
Languages : en
Pages : 87
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Book Description
With the most advanced and mature technology for electronic devices, silicon (Si) based devices can be processed with practically no material defects. However, Si technology has difficulty meeting the demand for some high-power, high-speed, and high-temperature applications due to limitations in its intrinsic properties. Wide bandgap semiconductors have greater prospects compared to Si based devices. The wide band gap material system shows higher breakdown voltage, lower leakage, higher saturation velocity, larger thermal conductivity and better thermal stability suitable for high-power, high-speed, and high-temperature operations of the devices. In recent years, GaN based devices have drawn much research attention due to their superior performances compared to other wide bandgap semiconductor (SiC) devices. Specifically, implementation of AlGaN/GaN high electron mobility transistor (HEMT) based power amplifiers have become very promising for applications in base stations or radar. With the increase in device power, channel temperature rises. This introduces high-temperature effects in the device characteristics. In addition, high-power, high-frequency and high-temperature operation of AlGaN/GaN HEMT is required for telemetry in extreme environment. AlGaN/GaN HEMT also shows great potential as chemically selective field-effect transistor (CHEMFET). Due to simpler imprint technique and amplification advantages CHEMFET based detection and characterization of bio-molecules has become very popular. AlGaN/GaN HEMT has high mobility two-dimensional electron gas (2 DEG) at the hetero-interface closer to the surface and hence it shows high sensitivity to any surface charge conditions. The primary objective of this research is to develop a temperature dependent physics based model of AlGaN/GaN HEMT to predict the performance for high-power and high-speed applications at varying temperatures. The physics based model has also been applied to predict the characteristics of AlGaN/GaN HEMT based CHEMFET for the characterization of bio-molecular solar batteries - Photosystem I reaction centers. Using the CHEMFET model, the number of reaction centers with effective orientation on the gate surface of the HEMT can be estimated.
Author: Christian Haupt
Publisher:
ISBN: 9783839603031
Category :
Languages : en
Pages : 175
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Book Description
In this work a scaling approach is studied to develop a transistor technology which achieves a high gain as well as a high output power at W-band frequencies and can be applied in the existing fabrication process for MMICs. Following the theoretical scaling rules for field effect transistors lateral and vertical critical dimensions of 100 nm and 10 nm must be achieved, respectively. Therefore various new fabrication processes were developed to enable the new critical dimensions with a sufficient production yield for MMIC fabrication. Transistors fabricated with these methods were evaluated regarding the influence of the scaled geometries on the device characteristics using S-parameter as well as DC-measurements. As a result a transistor technology could be established with a transconductance above 600 mS/mm which is one of the highest reported values for GaN-based HEMTs so far. Furthermore, these transistors feature a very low parasitic capacitance of 0.3 pF/mm and can as a consequence achieve a current-gain cut-off frequency of more than 110 GHz. Besides the high frequency characteristics short channel effects and their influence on the device characteristics were also evaluated. The scaled transistors are dominated by a drain induced barrier lowering (DIBL) and a critical aspect ratio of approximately 14 is necessary to suppress the DIBL-effect in GaN-HEMTs.
Author: Michael Hosch
Publisher: Cuvillier Verlag
ISBN: 3736938446
Category : Technology & Engineering
Languages : en
Pages : 129
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Book Description
This thesis deals with the analysis and optimization of some of the most prominent non-ideal effects in AlGaN/GaN high electron mobility transistors used in microwave applications as well as the optimization of the RF gain. The effect of current collapse, the root cause of leakage currents as well as field-dependent self-heating effects have been investigated by eletrical characterization using well established techniques and have been analyzed using 2-dimensional physical device simulations. It will be shown that the origin of all effects is strongly related to the device surface and some are even competing effects making device optimization a challenge. However, a detailed localization of the regions affecting device performance will be given leading to a better understanding for fabrication process optimization. Finally, I simulation study is conducted giving suggestions for RF gain improvement based on very simple device layout variations.
Author: Monta Raymond Holzworth (Jr)
Publisher:
ISBN:
Category :
Languages : en
Pages : 192
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Book Description
AlGaN/GaN high electron mobility transistors are unique for their combination of high temperature, high power, and high frequency applications. Compared to Si, Ge, and compound semiconductors such as GaAS and InP, AlGaN/GaN transistors outclass the current technology due to their superior combination of high breakdown voltage and high frequency performance. These characteristics arise from structural and electrical properties inherent to the AlGaN/GaN heterojunction which have enabled AlGaN/GaN transistors usage in important military and civilian applications such as microwave and millimeter technology, RADAR systems, and as high current and voltage switches in utility grid systems. As the technology continues to improve due to increased materials quality and device advancements, future applications will require AlGaN/GaN transistor usage under even higher voltages and temperatures. Therefore, the effects of these stresses need to be investigated in order improve device performance and reliability.
