Download or read book Device Characterization and Modeling of Large Size GaN HEMTs written by Jaime Alberto Zamudio Flores and published by kassel university press GmbH. This book was released on 2012-08-21 with total page 257 pages. Available in PDF, EPUB and Kindle. Book excerpt: This work presents a comprehensive modeling strategy for advanced large-size AlGaN/GaN HEMTs. A 22-element equivalent circuit with 12 extrinsic elements, including 6 capacitances, serves as small-signal model and as basis for a large-signal model. ANalysis of such capacitances leads to original equations, employed to form capacitance ratios. BAsic assumptions of existing parameter extractions for 22-element equivalent circuits are perfected: A) Required capacitance ratios are evaluated with device's top-view images. B) Influences of field plates and source air-bridges on these ratios are considered. The large-signal model contains a gate charge's non-quasi-static model and a dispersive-IDS model. THe extrinsic-to-intrinsic voltage transformation needed to calculate non-quasi-static parameters from small-signal parameters is improved with a new description for the measurement's boundary bias points. ALl IDS-model parameters, including time constants of charge-trapping and self-heating, are extracted using pulsed-DC IV and IDS-transient measurements, highlighting the modeling strategy's empirical character.

Download or read book Large Size AlGaN GaN HEMT Large Signal Electrothermal Characterization and Modeling for Wireless Digital Communications written by Samir Dahmani and published by . This book was released on 2011 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Parameter Extraction and Complex Nonlinear Transistor Models written by Gunter Kompa and published by Artech House. This book was released on 2019-12-31 with total page 610 pages. Available in PDF, EPUB and Kindle. Book excerpt: All model parameters are fundamentally coupled together, so that directly measured individual parameters, although widely used and accepted, may initially only serve as good estimates. This comprehensive resource presents all aspects concerning the modeling of semiconductor field-effect device parameters based on gallium-arsenide (GaAs) and gallium nitride (GaN) technology. Metal-semiconductor field-effect transistors (MESFETs), high electron mobility transistors (HEMTs) and heterojunction bipolar transistors (HBTs), their structures and functions, and existing transistor models are also classified. The Shockley model is presented in order to give insight into semiconductor field-effect transistor (FET) device physics and explain the relationship between geometric and material parameters and device performance. Extraction of trapping and thermal time constants is discussed. A special section is devoted to standard nonlinear FET models applied to large-signal measurements, including static-/pulsed-DC and single-/two-tone stimulation. High power measurement setups for signal waveform measurement, wideband source-/load-pull measurement (including envelope source-/load pull) are also included, along with high-power intermodulation distortion (IMD) measurement setup (including envelope load-pull). Written by a world-renowned expert in the field, this book is the first to cover of all aspects of semiconductor FET device modeling in a single volume.

Download or read book Large Signal Modeling of GaN Device for High Power Amplifier Design written by Anwar Hasan Jarndal and published by kassel university press GmbH. This book was released on 2006 with total page 136 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Advanced AlGaN GaN HEMT Technology Design Fabrication and Characterization written by Abel Fontserè Recuenco and published by . This book was released on 2014 with total page 240 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nowadays, the microelectronics technology is based on the mature and very well established silicon (Si) technology. However, Si exhibits some important limitations regarding its voltage blocking capability, operation temperature and switching frequency. In this sense, Gallium Nitride (GaN)-based high electron mobility transistors (HEMTs) devices have the potential to make this change possible. The unique combination of the high-breakdown field, the high-channel electron mobility of the two dimensional electron gas (2DEG), and high-temperature of operation has attracted enormous interest from social, academia and industry and in this context this PhD dissertation has been made. This thesis has focused on improving the device performance through the advanced design, fabrication and characterization of AlGaN/GaN HEMTs, primarily grown on Si templates. The first milestone of this PhD dissertation has been the establishment of a know-how on GaN HEMT technology from several points of view: the device design, the device modeling, the process fabrication and the advanced characterization primarily using devices fabricated at Centre de Recherche sur l'Hétéro-Epitaxie (CRHEA-CNRS) (France) in the framework of a collaborative project. In this project, the main workhorse of this dissertation was the explorative analysis performed on the AlGaN/GaN HEMTs by innovative electrical and physical characterization methods. A relevant objective of this thesis was also to merge the nanotechnology approach with the conventional characterization techniques at the device scale to understand the device performance. A number of physical characterization techniques have been imaginatively used during this PhD determine the main physical parameters of our devices such as the morphology, the composition, the threading dislocations density, the nanoscale conductive pattern and others. The conductive atomic force microscopy (CAFM) tool have been widely described and used to understand the conduction mechanisms through the AlGaN/GaN Ohmic contact by performing simultaneously topography and electrical conductivity measurements. As it occurs with the most of the electronic switches, the gate stack is maybe the critical part of the device in terms of performance and longtime reliability. For this reason, how the AlGaN/GaN HEMT gate contact affects the overall HEMT behaviour by means of advanced characterization and modeling has been intensively investigated. It is worth mentioning that the high-temperature characterization is also a cornerstone of this PhD. It has been reported the elevated temperature impact on the forward and the reverse leakage currents for analogous Schottky gate HEMTs grown on different substrates: Si, sapphire and free-standing GaN (FS-GaN). The HEMT' forward-current temperature coefficients (T̂a) as well as the thermal activation energies have been determined in the range of 25-300 oC. Besides, the impact of the elevated temperature on the Ohmic and gate contacts has also been investigated. The main results of the gold-free AlGaN/GaN HEMTs high-voltage devices fabricated with a 4 inch Si CMOS compatible technology at the clean room of the CNM in the framework of the industrial contract with ON semiconductor were presented. We have shown that the fabricated devices are in the state-of-the-art (gold-free Ohmic and Schottky contacts) taking into account their power device figure-of-merit ((VB̂2)/Ron) of 4.05×10̂8 W/cm̂2. Basically, two different families of AlGaN/GaN-on-Si MIS-HEMTs devices were fabricated on commercial 4 inch wafers: (i) using a thin ALD HfO2 (deposited on the CNM clean room) and (ii) thin in-situ grown Si3N4, as a gate insulator (grown by the vendor). The scientific impact of this PhD in terms of science indicators is of 17 journal papers (8 as first author) and 10 contributions at international conferences.

Download or read book Large signal Modeling of GaN HEMTs for Linear Power Amplifier Design written by Endalkachew Shewarega Mengistu and published by kassel university press GmbH. This book was released on 2008 with total page 153 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book GaN Based HEMTs for High Voltage Operation Design Technology and Characterization written by Eldad Bahat-Treidel and published by Cuvillier Verlag. This book was released on 2012-06-08 with total page 220 pages. Available in PDF, EPUB and Kindle. Book excerpt: Gallium nitride (GaN)-based High Electron Mobility Transistors (HEMTs) for high voltage, high power switching and regulating for space applications are studied in this work. Efficient power switching is associated with operation in high OFF-state blocking voltage while keeping the ON-state resistance, the dynamic dispersion and leakage currents as low as possible. The potential of such devices to operate at high voltages is limited by a chain of factors such as subthreshold leakages and the device geometry. Blocking voltage enhancement is a complicated problem that requires parallel methods for solution; epitaxial layers design, device structural and geometry design, and suitable semiconductor manufacturing technique. In this work physical-based device simulation as an engineering tool was developed. An overview on GaN-based HEMTs physical based device simulation using Silvaco-“ATLAS” is given. The simulation is utilized to analyze, give insight to the modes of operation of the device and for design and evaluation of innovative concepts. Physical-based models that describe the properties of the semiconductor material are introduced. A detailed description of the specific AlGaN/GaN HEMT structure definition and geometries are given along with the complex fine meshing requirements. Nitride-semiconductor specific material properties and their physical models are reviewed focusing on the energetic band structure, epitaxial strain tensor calculation in wurtzite materials and build-in polarization models. Special attention for thermal conductivity, carriers’ mobility and Schottky-gate-reverse-bias-tunneling is paid. Empirical parameters matching and adjustment of models parameters to match the experimental device measured results are discussed. An enhancement of breakdown voltage in AlxGa1-xN/GaN HEMT devices by increasing the electron confinement in the transistor channel using a low Al content AlyGa1-yN back-barrier layer structure is systematically studied. It is shown that the reduced sub-threshold drain-leakage current through the buffer layer postpones the punch-through and therefore shifts the breakdown of the device to higher voltages. It is also shown that the punch-through voltage (VPT) scales up with the device dimensions (gate to drain separation). An optimized electron confinement results both, in a scaling of breakdown voltage with device geometry and a significantly reduced sub-threshold drain and gate leakage currents. These beneficial properties are pronounced even further if gate recess technology is applied for device fabrication. For the systematic study a large variations of back-barrier epitaxial structures were grown on sapphire, n-type 4H-SiC and semi-insulating 4H-SiC substrates. The devices with 5 μm gate-drain separation grown on n-SiC owning Al0.05Ga0.95N and Al0.10Ga0.90N back-barrier exhibit 304 V and 0.43 m × cm2 and 342 V and 0.41 m × cm2 respectively. To investigate the impact of AlyGa1-yN back-barrier on the device properties the devices were characterized in DC along with microwave mode and robustness DC-step-stress test. Physical-based device simulations give insight in the respective electronic mechanisms and to the punch-through process that leads to device breakdown. Systematic study of GaN-based HEMT devices with insulating carbon-doped GaN back-barrier for high voltage operation is also presented. Suppression of the OFF-state sub-threshold drain leakage-currents enables breakdown voltage enhancement over 1000 V with low ON-state resistance. The devices with 5 μm gate-drain separation on SI-SiC and 7 μm gate-drain separation on n-SiC exhibit 938 V and 0.39 m × cm2 and 942 V and 0.39 m × cm2 respectively. Power device figure of merit of ~2.3 × 109 V2/-cm2 was calculated for these devices. The impacts of variations of carbon doping concentration, GaN channel thickness and substrates are evaluated. Trade-off considerations in ON-state resistance and of current collapse are addressed. A novel GaN-based HEMTs with innovative planar Multiple-Grating-Field-Plates (MGFPs) for high voltage operation are described. A synergy effect with additional electron channel confinement by using a heterojunction AlGaN back-barrier is demonstrated. Suppression of the OFF-state sub-threshold gate and drain leakage-currents enables breakdown voltage enhancement over 700 V and low ON-state resistance of 0.68 m × cm2. Such devices have a minor trade-off in ON-state resistance, lag factor, maximum oscillation frequency and cut-off frequency. Systematic study of the MGFP design and the effect of Al composition in the back-barrier are described. Physics-based device simulation results give insight into electric field distribution and charge carrier concentration depending on field-plate design. The GaN superior material breakdown strength properties are not always a guarantee for high voltage devices. In addition to superior epitaxial growth design and optimization for high voltage operation the device geometrical layout design and the device manufacturing process design and parameters optimization are important criteria for breakdown voltage enhancement. Smart layout prevent immature breakdown due to lateral proximity of highly biased interconnects. Optimization of inter device isolation designed for high voltage prevents substantial subthreshold leakage. An example for high voltage test device layout design and an example for critical inter-device insulation manufacturing process optimization are presented. While major efforts are being made to improve the forward blocking performance, devices with reverse blocking capability are also desired in a number of applications. A novel GaN-based HEMT with reverse blocking capability for Class-S switch-mode amplifiers is introduced. The high voltage protection is achieved by introducing an integrated recessed Schottky contact as a drain electrode. Results from our Schottky-drain HEMT demonstrate an excellent reverse blocking with minor trade-off in the ON-state resistance for the complete device. The excellent quality of the forward diode characteristics indicates high robustness of the recess process. The reverse blocking capability of the diode is better than –110 V. Physical-based device simulations give insight in the respective electronic mechanisms. Zusammenfassung In dieser Arbeit wurden Galliumnitrid (GaN)-basierte Hochspannungs-HEMTs (High Electron Mobility Transistor) für Hochleistungsschalt- und Regelanwendungen in der Raumfahrt untersucht. Effizientes Leistungsschalten erfordert einen Betrieb bei hohen Sperrspannungen gepaart mit niedrigem Einschaltwiderstand, geringer dynamischer Dispersion und minimalen Leckströmen. Dabei wird das aus dem Halbleitermaterial herrührende Potential für extrem spannungsfeste Transistoren aufgrund mehrerer Faktoren aus dem lateralen und dem vertikalen Bauelementedesign oft nicht erreicht. Physikalisch-basierte Simulationswerkzeuge für die Bauelemente wurden daher entwickelt. Die damit durchgeführte Analyse der unterschiedlichen Transistorbetriebszustände ermöglichte das Entwickeln innovativer Bauelementdesignkonzepte. Das Erhöhen der Bauelementsperrspannung erfordert parallele und ineinandergreifende Lösungsansätze für die Epitaxieschichten, das strukturelle und das geometrische Design und für die Prozessierungstechnologie. Neuartige Bauelementstrukturen mit einer rückseitigen Kanalbarriere (back-barrier) aus AlGaN oder Kohlenstoff-dotierem GaN in Kombination mit neuartigen geometrischen Strukturen wie den Mehrfachgitterfeldplatten (MGFP, Multiple-Grating-Field-Plate) wurden untersucht. Die elektrische Gleichspannungscharakterisierung zeigte dabei eine signifikante Verringerung der Leckströme im gesperrten Zustand. Dies resultierte bei nach wie vor sehr kleinem Einschaltwiderstand in einer Durchbruchspannungserhöhung um das etwa Zehnfache auf über 1000 V. Vorzeitige Spannungsüberschläge aufgrund von Feldstärkenspitzen an Verbindungsmetallisierungen werden durch ein geschickt gestaltetes Bauelementlayout verhindert. Eine Optimierung der Halbleiterisolierung zwischen den aktiven Strukturen führte auch im kV-Bereich zu vernachlässigbaren Leckströme. Während das Hauptaugenmerk der Arbeit auf der Erhöhung der Spannungsfestigkeit im Vorwärtsbetrieb des Transistors lag, ist für einige Anwendung auch ein rückwärtiges Sperren erwünscht. Für Schaltverstärker im S-Klassenbetrieb wurde ein neuartiger GaN-HEMT entwickelt, dessen rückwärtiges Sperrverhalten durch einen tiefgelegten Schottkykontakt als Drainelektrode hervorgerufen wird. Eine derartige Struktur ergab eine rückwärtige Spannungsfestigkeit von über 110 V.

Download or read book Trapping Effects in AlGaN GaN HEMTs for High Frequency Applications written by Chieh Kai Yang and published by . This book was released on 2011 with total page 109 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: Any defect site existing in the AlGaN/GaN HEMTs can be electrically active during device operation. The activated defect site not only could lead to a degradation in the output characteristics but may introduce additional nonlinearity which seriously downgrades the values of devices for various applications. This motivates us to study the detailed path experimentally and theoretically how an electrically-activated defect site could impact the device performances during practical device operation. In this study, the g oal is (1) to give device engineers ideas on how further improvements can be devised to strengthen the existing GaN technology and (2) to provide circuit designers with better understanding on how to use GaN devices more efficiently for the development of reliable commercial GaN products for higher power applications in wireless systems. Single tone characterization results of AlGaN/GaN HEMTs for Class A operation are presented and compared. A new combined large signal network analyzer / deep level optical spectroscopy system is utilized to study the impact of illumination on the CW large-signal load line and small-signal S-parameters variations to identify the possible energy level of the trapping center responsible for the degradation of the device performance. A new pulsed-IV pulsed-RF "coldFET" technique is introduced to extract parasitic elements existing in the access regions of AlGaN/GaN HEMTs. The observation of bias-dependence is detailed and a simple semi-physical model is proposed which provides a satisfactory description of experimental results. The low-frequency noise, an important figure of merit in terms of reliability, is briefly-reviewed. Additive phase noise measurements are presented and the effects of illumination and load impedance are examined. A physical expression is derived and simulated which successfully establishes a relationship between the access resistance and the low-frequency noise and provides a qualitative description of the measurement results.

Download or read book Wide Bandgap SiC GaN Power Devices Characterization and Modeling written by Ke Li and published by . This book was released on 2014 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Compared to traditional silicon (Si) semiconductor material, wide bandgap (WBG) materials like silicon carbide (SiC) and gallium nitride are gradually applied to fabricate power semiconductor devices, which are used in power converters to achieve high power efficiency, high operation temperature and high switching frequency. As those power devices are relatively new, their characterization and modeling are important to better understand their characteristics for better use. This dissertation is mainly focused on those WBG power semiconductor devices characterization, modeling and fast switching currents measurement. In order to measure their static characteristics, a single-pulse method is presented. A SiC diode and a "normally-off" SiC JFET is characterized by this method from ambient temperature to their maximal junction temperature with the maximal power dissipation around kilowatt. Afterwards, in order to determine power device inter-electrode capacitances, a measurement method based on the use of multiple current probes is proposed and validated by measuring inter-electrode capacitances of power devices of different technologies. Behavioral models of a Si diode and the SiC JFET are built by using the results of the above characterization methods, by which the evolution of the inter-electrode capacitances for different operating conditions are included in the models. Power diode models are validated with the measurements, in which the current is measured by a proposed current surface probe.

Download or read book Advanced SPICE Model for GaN HEMTs ASM HEMT written by Sourabh Khandelwal and published by Springer Nature. This book was released on 2022-01-01 with total page 194 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book discusses in detail the Advanced SPICE Model for GaN HEMTs (ASM-HEMT), a new industry standard model for GaN-based power and RF circuit design. The author describes this new, standard model in detail, covering the different components of the ASM GaN model from fundamental derivations to the implementation in circuit simulation tools. The book also includes a detailed description of parameter extraction steps and model quality tests, which are critically important for effective use of this standard model in circuit simulation and product design. Coverage includes both radio-frequency (RF), and power electronics applications of this model. Practical issues related to measurement data and parameter extraction flow are also discussed, enabling readers easily to adopt this new model for design flow and simulation tools. Describes in detail a new industry standard for GaN-based power and RF circuit design; Includes discussion of practical problems and their solutions in GaN device modeling; Covers both radio-frequency (RF) and power electronics application of GaN technology; Describes modeling of both GaN RF and power devices.

Download or read book Wide Bandgap Semiconductor Based Micro Nano Devices written by Jung-Hun Seo and published by MDPI. This book was released on 2019-04-25 with total page 138 pages. Available in PDF, EPUB and Kindle. Book excerpt: While group IV or III-V based device technologies have reached their technical limitations (e.g., limited detection wavelength range or low power handling capability), wide bandgap (WBG) semiconductors which have band-gaps greater than 3 eV have gained significant attention in recent years as a key semiconductor material in high-performance optoelectronic and electronic devices. These WBG semiconductors have two definitive advantages for optoelectronic and electronic applications due to their large bandgap energy. WBG energy is suitable to absorb or emit ultraviolet (UV) light in optoelectronic devices. It also provides a higher electric breakdown field, which allows electronic devices to possess higher breakdown voltages. This Special Issue seeks research papers, short communications, and review articles that focus on novel synthesis, processing, designs, fabrication, and modeling of various WBG semiconductor power electronics and optoelectronic devices.

Download or read book Multiphysics Characterization of GaN HEMTs Via Micro Raman Spectroscopy written by Kevin Robert Bagnall and published by . This book was released on 2017 with total page 226 pages. Available in PDF, EPUB and Kindle. Book excerpt: Microelectronic devices based on solid-state transistor technology are a key innovation that have transformed modern society and affected many aspects of our daily lives. As we continue to increase the density and functionality of transistors, progress is limited by the intrinsic material properties of the most common semiconductor, silicon (Si). Therefore, there is an increasing need for compound semiconductor technologies with more favorable material properties, such as gallium nitride (GaN) high electron mobility transistors (HEMTs), which can operate at significantly higher voltages, current densities, and power densities than Si-based field effect transistors of the same size. However, these more strenuous operating conditions combined with the desire to operate GaN HEMTs in harsher environmental conditions lead to elevated channel temperatures, reduced device performance, and premature device failure. Thus, there is a great need to develop modeling and experimental approaches to characterize the temperature, structural evolution, and electrical performance of GaN HEMTs with microscale and even nanoscale spatial resolution. This thesis explores the application of micro-Raman spectroscopy to experimental characterization of temperature, stress, strain, and electric field in GaN HEMTs with ~1 pim spatial and ~30 ns temporal resolution, respectively. Although micro-Raman spectroscopy has been one of the most common experimental techniques for measuring temperature and stress in GaN HEMTs for the last fifteen years, many of the previous works in the field have been empirical and unable to satisfactorily explain basic features of the Raman response of HEMTs under bias. This thesis demonstrates for the first time the correct electric field dependence of the optical phonon frequencies of wurtzite GaN and measurement of the electric field along the c-axis of the GaN buffer in HEMTs biased in the pinched OFF state. With this holistic understanding of the phonon frequency dependence on temperature, stress, electric field, and strain, a methodology for simultaneously measuring temperature, stress, and electric field using the shift of three Raman peaks has been developed. Theoretical and experimental characterization of the fundamental transient thermal response of GaN HEMTs is also presented using time-resolved micro-Raman thermometry. The novel developments in this thesis represent a new "multiphysics" approach to microscale characterization of semiconductor devices, which we anticipate to have a significant impact in developing a more mechanistic and physics-based approach to transistor reliability rather than relying merely upon the statistics of a population of devices. Such an approach, we believe, will enable new semiconductor devices with unprecedented reliability and performance.

Download or read book Simulation of Short Channel AlGaN GaN HEMTs written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The increasing data rates demanded by third generation cellular communication systems and other high frequency applications require the use of power amplifiers operating at frequencies exceeding 1 GHz with output of the order of hundreds to thousands of watts. The area of very high frequency, very high power electronics is currently dominated by vacuum tube based devices as conventional semiconductor devices suffer from relatively low breakdown voltages precluding their operation at very high voltages and high powers. The vacuum tube based devices, however, suffer from the issues of high cost, large size and reliability issues. In recent years AlGaN/GaN HEMTs have demonstrated output power densities as high as 11 W/mm operating at microwave frequencies greater than 10 GHz. The extremely high output power density levels are achieved due to the high breakdown voltages of these wide bandgap devices and due to the large polarization induced charge leading to high output current densities. This work investigates the performance of the AlGaN/GaN HEMT using device modeling. Polarization effects have been incorporated using a highly doped AlGaN spacer layer. This thesis examines the effect of the device structure and doping profile on the AlGaN/GaN HEMT's microwave performance including the unilateral power gain and maximum frequency of oscillation.

Download or read book Power GaN Devices written by Matteo Meneghini and published by Springer. This book was released on 2016-09-08 with total page 383 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents the first comprehensive overview of the properties and fabrication methods of GaN-based power transistors, with contributions from the most active research groups in the field. It describes how gallium nitride has emerged as an excellent material for the fabrication of power transistors; thanks to the high energy gap, high breakdown field, and saturation velocity of GaN, these devices can reach breakdown voltages beyond the kV range, and very high switching frequencies, thus being suitable for application in power conversion systems. Based on GaN, switching-mode power converters with efficiency in excess of 99 % have been already demonstrated, thus clearing the way for massive adoption of GaN transistors in the power conversion market. This is expected to have important advantages at both the environmental and economic level, since power conversion losses account for 10 % of global electricity consumption. The first part of the book describes the properties and advantages of gallium nitride compared to conventional semiconductor materials. The second part of the book describes the techniques used for device fabrication, and the methods for GaN-on-Silicon mass production. Specific attention is paid to the three most advanced device structures: lateral transistors, vertical power devices, and nanowire-based HEMTs. Other relevant topics covered by the book are the strategies for normally-off operation, and the problems related to device reliability. The last chapter reviews the switching characteristics of GaN HEMTs based on a systems level approach. This book is a unique reference for people working in the materials, device and power electronics fields; it provides interdisciplinary information on material growth, device fabrication, reliability issues and circuit-level switching investigation.

Download or read book Modeling and Characterization of Circuit Level Transients in Wide Bandgap Devices written by Naga Babu Koganti and published by . This book was released on 2018 with total page 92 pages. Available in PDF, EPUB and Kindle. Book excerpt: Wide bandgap devices (GaN) are an enabling technology for high frequency and high efficiency power electronics. Especially, the combination of low on-resistance and high breakdown voltages relates to high power-density capabilities of GaN devices and makes them a potential alternative for silicon devices in high power conversion applications. Also, GaN devices are intrinsically very fast with low switching losses due to high saturation velocities and can achieve higher efficiencies in hard switching applications. On the contrary, low inherent capacitance makes them more vulnerable to high dv/dt transitions and can cause undesired circuit level issues such as voltage overshoot, ringing and false turn-on. Any unchecked external parasitic impedances will further exacerbate the device transient behavior and run the risk of device failure under circuit level implementation. Therefore, this thesis work presents a detailed analytical framework to address some of the circuit level challenges associated with GaN. The analytical framework lays a foundation to optimize device safety and performance. The first part of this thesis work deals with mitigation of false turn-on of the synchronous-FET in a half bridge buck converter operated at 1 MHz frequency. The study presents a detail investigation of false turn-on event and proposes its mitigation by modifying the control-FET gate resistance. An analytical circuit model with intrinsic device components and external parasitic parameters has been considered to develop a relationship between control-FET gate resistance and false turn-on induced voltage of the synchronous-FET. The results of the analytical method proposed in this study show good agreement with the experimental results. The model can then be used to predict false turn-on at varying values of high-side gate resistance. The second part of this thesis focuses on development of an improved model to predict voltage overshoot in normally off GaN devices. As the GaN device requires lower gate bias to fully turn-on when compared to its counterpart (Si), there is a narrow margin between recommended (5V) and max gate voltage rating (6V). Any voltage spike beyond the maximum gate voltage could cause device breakdown and catastrophic failure. Therefore, to avoid such failures and safeguard the GaN device, proper prediction methodologies are required. In this study a higher order (fourth order) analytical method is developed that allows for the calculation of gate resistances necessary for a desired amount of overshoot. The non-linear capacitances of the device are modeled and considered in the analysis. The model is validated with a double-pulse tester and a boost converter. The developed method was compared with known second order and circuit simulation models and found to yield improved results. The two studies detailed here lay the foundation for optimizing the performance of GaN devices while keeping them in their safe operating regions.

Download or read book Temperature Dependent Analytical Modeling Simulation and Characterizations of HEMTs in Gallium Nitride Process written by Hasina F. Huq and published by . This book was released on 2006 with total page 146 pages. Available in PDF, EPUB and Kindle. Book excerpt: Research is being conducted for a high-performance building block for high frequency and high temperature applications that combine lower costs with improved performance and manufacturability. Researchers have focused their attention on new semiconductor materials for use in device technology to address system improvements. Of the contenders, silicon carbide (SiC), gallium nitride (GaN), and diamond are emerging as the front-runners. GaN-based electronic devices, AlGaN/GaN heterojunction field effect transistors (HFETs), are the leading candidates for achieving ultra-high frequency and high-power amplifiers. Recent advances in device and amplifier performance support this claim. GaN is comparable to the other prominent material options for high-performance devices. The dissertation presents the work on analytical modeling and simulation of GaN high power HEMT and MOS gate HEMT, model verification with test data and device characterization at elevated temperatures. The model takes into account the carrier mobility, the doping densities, the saturation velocity, and the thickness of different layers. Considering the GaN material processing limitations and feedback from the simulation results, an application specific AlGaN/GaN RF power HEMT structure has been proposed. The doping concentrations and the thickness of various layers are selected to provide adequate channel charge density for the proposed devices. A good agreement between the analytical model, and the experimental data is demonstrated. The proposed temperature model can operate at higher voltages and shows stable operation of the devices at higher temperatures. The investigated temperature range is from 100°K to 600°K. The temperature models include the effect of temperature variation on the threshold voltage, carrier mobility, bandgap and saturation velocity. The calculated values of the critical parameters suggest that the proposed device can operate in the GHz range for temperature up to 600°K, which indicates that the device could survive in extreme environments. The models developed in this research will not only help the wide bandgap device researchers in the device behavioral study but will also provide valuable information for circuit designers.

Download or read book Microwave De embedding written by Ernesto Limiti and published by Elsevier Inc. Chapters. This book was released on 2013-11-09 with total page 84 pages. Available in PDF, EPUB and Kindle. Book excerpt: An overview of topics is presented related to noise characterization and modeling of linear, active devices for microwave applications, as well as to advanced methodologies for low-noise design. A complete description of the most common noise measurement techniques, namely the Y-factor method and the cold source method, are provided, with particular attention being paid to practical aspects such as de-embedding the measurement at the device under test reference planes, possible sources of error, and uncertainty estimation. Noise modeling is approached from a well-established standpoint, based on the extraction of a small-signal equivalent circuit model; but also source pull-based techniques—both standard and advanced ones—are broadly illustrated. Finally, a comprehensive discussion on design of single- and multistage low-noise amplifiers is proposed, ranging from the most classical tools and methodologies, such as constant-gain and constant-noise circles, to novel graphical tools and more advanced concepts, such as global mismatch limits and noise measure.