Fundamentals of Power Semiconductor Devices

B. Jayant Baliga

Fundamentals of PowerSemiconductor Devices

Second Edition

B. Jayant BaligaRaleigh, NC, USA

ISBN 978-3-319-93987-2 ISBN 978-3-319-93988-9 (eBook)https://doi.org/10.1007/978-3-319-93988-9

Library of Congress Control Number: 2018948141

© Springer International Publishing AG, part of Springer Nature 2008, 2019This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or partof the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations,recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission orinformation storage and retrieval, electronic adaptation, computer software, or by similar or dissimilarmethodology now known or hereafter developed.The use of general descriptive names, registered names, trademarks, service marks, etc. in thispublication does not imply, even in the absence of a specific statement, that such names are exemptfrom the relevant protective laws and regulations and therefore free for general use.The publisher, the authors, and the editors are safe to assume that the advice and information in this bookare believed to be true and accurate at the date of publication. Neither the publisher nor the authors or theeditors give a warranty, express or implied, with respect to the material contained herein or for any errorsor omissions that may have been made. The publisher remains neutral with regard to jurisdictional claimsin published maps and institutional affiliations.

This Springer imprint is published by Springer Nature, under the registered company SpringerInternational Publishing AGThe registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland

The author would like to dedicate this bookto his wife, Pratima, for her unwaveringsupport throughout his career devoted tothe enhancement of the performance andunderstanding of power semiconductordevices.

Preface to the Second Edition

The first 300 copies of Fundamentals of Power Semiconductor Devices printed in2008 were immediately sold after its publication, and the book was declared a “bestseller” on Amazon. Over 2000 hard copies of the book have been sold since then – aremarkable number for a book on a very specialized topic in the semiconductor field.According to the publisher, Springer Science þ Business Media, more than 46,000chapter downloads of this book have occurred since its publication, placing it amongthe top 25% of downloaded e-books. In addition, Springer ScienceþBusinessMediaauthorized an edition translated intoChinese in 2013which has sold over 2000 copies.

I am gratified that my book has been adopted around the world as a textbook at allthe universities that teach this subject matter in the electrical engineering curriculum.This provides validation that the didactic treatment of the physics of power semi-conductor devices in this book is easy to comprehend and that the extensiveanalytical models provided in the book are amenable to classroom instruction. Ihave personally used this tome as my textbook for teaching a graduate course duringthe last 10 years at the North Carolina State University with very satisfactoryresponse from the students.

Preparing any book of over 1000 pages is fraught with the peril of typographicalerrors and occasional inconsistencies in the nomenclature. In addition, it becameapparent to me that I had not included some topics worthy of discussion in the book.Consequently, I was pleased to get a very positive response from the editorialdirector, Chuck Glaser, at Springer-Science to develop a “second edition” of thebook. Due to advances in printing technology, he encouraged me to use coloredillustrations for the new edition to enhance the clarity of the knowledge beingimparted. In response, I have redrawn most of the figures in color for this bookwhich should make the material easier to assimilate by the reader.

The second edition contains new information and models in all the chapters. Forthose who are already familiar with the first edition, it may be useful to specificallyenumerate the changes made in each chapter.

In Chap. 1, “Introduction,” additional references have been provided for readersto obtain information on the charge-coupled devices not treated in this book.

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In Chap. 2 on “Material Properties,” temperature dependence of the impactionization coefficients in semiconductors has been added.

In Chap. 3 on “Breakdown Voltage,” the analytical model has been improved tomatch experimental results for silicon devices by using Baliga’s power law for theimpact ionization coefficient in place of Fulop’s law. Temperature dependence of thebreakdown voltage of silicon devices has been added. New edge terminations thathave been developed for obtaining close to ideal breakdown voltage in siliconcarbide power devices have been described. A model for estimation of the spaceoccupied by the edge termination has been created.

In Chap. 4 on “Schottky Rectifiers,” a new section has been added to analyze thereverse recovery current flow during turn-off. An analytical model has been pro-vided for computation of the dependence of the reverse recovery current transient onthe rate of change in the anode voltage.

In Chap. 5 on “P-i-N Rectifiers,” the model for reverse recovery current has beenimproved. New sections have been added to discuss the safe operating area andcreate a model for the maximum allowable rate of change of device current duringreverse recovery turn-off.

In Chap. 6 on “Power MOSFETs,” novel device structures and additional ana-lytical models have been added. The ideal specific on-resistance for silicon deviceshas been revised by using Baliga’s power law for the impact ionization coefficient insilicon. The recently developed silicon carbide JBSFET structure, in which theSchottky reverse conducting diode is integrated with the MOSFET cells, has beenincluded as an important device for applications in inverters for solar power andmotor control. A novel silicon carbide bidirectional field-effect transistor (BiDFET)is also discussed here because it provides an ideal switch for creating matrixconverters. An analytical model for turn-off of power MOSFETs with unclampedinductive load has been provided because this capability is now expected for thesedevices in applications.

In Chap. 7 on “Bipolar Junction Transistors,” a more accurate model for thevoltage rise during turn-off has been included.

In Chap. 8 on “Thyristors,” the turn-off model for the GTO has been improved.In Chap. 9 on “Insulated Gate Bipolar Transistors,” the model for leakage current

has been improved. An analytical model for turn-off in soft-switching circuits hasbeen added because this type of operation allows reducing turn-off losses so that thedevice can be used at higher frequencies.

In the concluding Chap. 10, “Synopsis,” an extensive discussion of the socialimpact of power devices has been added. These devices are now required in everysector of our economy to improve the quality of life for people around the worldwhile providing the economic benefits of reduced energy consumption by enhancingthe efficiency. This reduction in energy consumption has been found to eliminate theemission of over 100 trillion pounds of carbon dioxide mitigating its impact onglobal warming.

During the preparation of the first edition of Fundamentals of Power Semicon-ductor Devices for publication in 2008, I found that it is not possible to include manyof the advanced concepts that had emerged to achieve dramatic improvements in the

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performance of silicon power devices because the book was already over 1000 pagesin length. In order to create a comprehensive treatment of these advances, I prepareda series of books published by Springer-Science over the next several years.

Advanced Power Rectifier Concepts was published in 2009 to provide a rigoroustreatment of the JBS and MPS rectifiers which combine the physics of P-N junctionsand Schottky contacts. The book also describes the revolutionary concept oftwo-dimensional charge coupling to dramatically reduce the resistance of the driftregion in power rectifiers. New analytical models for these devices were provided forthe first time supported by the results of numerical simulations. This book wasimportant because these devices became commercially available for power supplyapplications.

Advanced Power MOSFET Concepts was published in 2010 to introduce readersto the benefits of the two-dimensional charge-coupling concept for powerMOSFETs. The analysis of the conventional devices was included in this book toprovide a baseline for evaluation of the improved technology. Both static anddynamic performance was analytically modeled with validation from numericalsimulations. The benefits of using silicon carbide material for power MOSFETdevices were also provided in this book. The relative performance of all the deviceswas compared over a breakdown voltage range from 10 to 1000 V.

Advanced High Voltage Power Device Concepts was published in 2011 to createa didactic resource for devices with breakdown voltages above 1000 V. This treatiseincluded silicon thyristors (and GTOs) and IGBTs as commercially available bench-mark devices. The silicon MOS-gated thyristors (MCTs, BRTs, and ESTs) wereincluded in the book as advanced concepts with improved performance that have notbe capitalized by the industry. A significant portion of the book was devoted toemerging silicon carbide power MOSFETs that have already been commercializedfor motor control and solar inverter applications and silicon carbide IGBTs that showpromise for utility applications in the future.

Readers of this book are encouraged to peruse the above books to gain acomprehensive knowledge of all the power semiconductor devices that are havingan impact on our lives.

In conclusion, it has been my privilege to devote my entire career over a time spanof over four decades on power semiconductor devices. I was fortunate to proposedtwo groundbreaking innovations in the 1979–1980 time frame. My first idea was tomerge MOS and bipolar physics to create the insulated gate bipolar transistor (IGBT)and rapidly commercialize it at GE between 1981 and 1983. This innovationrevolutionized power electronics transforming it from analog to digital control ofpower. My second idea, based on deriving a relationship (Baliga’s figure of merit)between the resistance of the drift region of power devices and the basic semi-conductor material properties for the first time, demonstrated that a 1000-foldenhancement could be achieved by replacing silicon with silicon carbide. Thecommercialization of this approach took more than 30 years to improve the materialquality and bring down its cost. It is immensely gratifying to me that we are now atthe cusp of making this technology commercially viable, creating another revolu-tionary advancement in power electronic systems.

Preface to the Second Edition ix

Many other ideas of mine, such as the JBS rectifier, the TMBS rectifier, thesuperlinear MOSFET, the SSCFET, the JBSFET, and the GD-MOSFET, have alsobeen commercialized for various applications. I want to take this opportunity toappreciate the contribution of thousands of engineers who have been responsible forusing my ideas for generating so many products over the years.

Raleigh, NC, USA B. Jayant BaligaDecember 2007

x Preface to the Second Edition

Preface to the First Edition

Today the semiconductor business exceeds $ 200 billion with about 10 percent of therevenue derived from power semiconductor devices and smart power integratedcircuits. Power semiconductor devices are recognized as a key component of allpower electronic systems. It is estimated that at least 50 percent of the electricityused in the world is controlled by power devices. With the wide spread use ofelectronics in the consumer, industrial, medical, and transportation sectors, powerdevices have a major impact on the economy because they determine the cost andefficiency of systems. After the initial replacement of vacuum tubes by solid statedevices in the 1950s, semiconductor power devices have taken a dominant role withsilicon serving as the base material. These developments have been referred to as theSecond Electronic Revolution.

Bipolar power devices, such as bipolar transistors and thyristors, were firstdeveloped in the 1950s. Due to the many advantages of semiconductor deviceswhen compared with vacuum tubes, there was a constant demand for increasing thepower ratings of these devices. Their power ratings and switching frequencyincreased with advancements in the understanding of the operating physics, theavailability of larger diameter, high resistivity silicon wafers, and the introductionof more advanced lithography capability. During the next 20 years, the technologyfor the bipolar devices reached a high degree of maturity. By the 1970s, bipolarpower transistors with current handling capability of hundreds of amperes andvoltage blocking capability of over 500 volts became available. More remarkably,technology was developed capable of manufacturing an individual power thyristorfrom an entire 4-inch diameter silicon wafer with voltage rating over 5000 volts.

My involvement with power semiconductor devices began in 1974 when I washired by the General Electric Company at their corporate research and developmentcenter to start a new group to work on this technology. At that time, I had justcompleted my Ph.D. degree at Rensselaer Polytechnic Institute by performingresearch on a novel method for the growth of epitaxial layers of compound semi-conductors [1–4]. Although I wanted to continue to explore this approach afterjoining the semiconductor industry, I was unable to secure a position at any of the

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major research laboratories due to a lack of interest in this unproven growthtechnology. Ironically, the OMCVD epitaxial growth process that I pioneered withProfessor Ghandhi has now become the most commonly used method for the growthof high quality compound semiconductor layers for applications such as lasers,LEDs and microwave transistors.

My first assignment at GE was to develop improved processes for the fabricationof high voltage thyristors used in their power distribution business. Since thethyristors were used for high voltage DC transmission and electric locomotivedrives, the emphasis was on increasing the voltage rating and current handlingcapability. The ability to use neutron transmutation doping to produce high resistiv-ity n-type silicon with improved uniformity across large diameter wafers became ofinterest at this time. I was fortunate in making some of the critical contributions toannealing the damage caused to the silicon lattice during neutron irradiation makingthis process commercially viable [5]. This enabled increasing the blocking voltage ofthyristors to over 5000 volts while being able to handle over 2000 amperes of currentin a single device.

Meanwhile, bipolar power transistors were being developed with the goal ofincreasing the switching frequency in medium power systems. Unfortunately, thecurrent gain of bipolar transistors was found to be low when it was designed for highvoltage operation at high current density. The popular solution to this problem, usingthe Darlington configuration, had the disadvantage of increasing the on-state voltagedrop resulting in an increase in the power dissipation. In addition to the large controlcurrents required for bipolar transistors, they suffered from poor safe-operating-areadue to second breakdown failure modes. These issues produced a cumbersomedesign, with snubber networks, that raised the cost and degraded the efficiency ofthe power control system.

In the 1970s, the power MOSFET product was first introduced by InternationalRectifier Corporation. Although initially hailed as a replacement for all bipolarpower devices due to its high input impedance and fast switching speed, thepower MOSFET has successfully cornered the market for low voltage (<100 V)and high switching speed (>100 kHz) applications but failed to make serious inroadsin the high voltage arena. This is because the on-state resistance of power MOSFETsincreases very rapidly with increase in the breakdown voltage. The resulting highconduction losses, even when using larger more expensive die, degrade the overallsystem efficiency.

In recognition of these issues, I proposed two new thrusts in 1979 for the powerdevice field. The first was based upon the merging of MOS and bipolar devicephysics to create a new category of power devices [6]. My most successful innova-tion among MOS-Bipolar devices has been the Insulated Gate Bipolar Transistor(IGBT). Soon after commercial introduction in the early 1980s, the IGBT wasadopted for all medium power electronic applications. Today, it is manufacturedby more than a dozen companies around the world for consumer, industrial, medical,and other applications that benefit society. The triumph of the IGBT is associatedwith its huge power gain, high input impedance, wide safe operating area, and a

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switching speed that can be tailored for applications depending upon their operatingfrequency.

The second approach that I suggested in 1979 for enhancing the performance ofpower devices was to replace silicon with wide band gap semiconductors. The basisfor this approach was an equation that I derived relating the on-resistance of the driftregion in unipolar power devices to the basic properties of the semiconductormaterial. This equation has since been referred to as Baliga’s Figure of Merit(BFOM). In addition to the expected reduction in the on-state resistance with highercarrier mobility, the equation predicts a reduction in on-resistance as the inverse ofthe cube of the breakdown electric field strength of the semiconductor material.

The first attempt to develop wide band gap semiconductor based power deviceswas undertaken at the General Electric Corporate Research and Development Cen-ter, Schenectady, NY, under my direction. The goal was to leverage a 13-foldreduction in specific on-resistance for the drift region predicted by the BFOM forGallium Arsenide. A team of 10 scientists was assembled to tackle the difficultproblems of the growth of high resistivity epitaxial layers, the fabrication of lowresistivity ohmic contacts, low leakage Schottky contacts, and the passivation of theGaAs surface. This led to an enhanced understanding of the breakdown strength[7] for GaAs and the successful fabrication of high performance Schottky rectifiers[8] and MESFETs [9]. Experimental verification of the basic thesis of the analysisrepresented by BFOM was therefore demonstrated during this period. CommercialGaAs based Schottky rectifier products were subsequently introduced in the marketby several companies.

In the later half of the 1980s, the technology for the growth of silicon carbide wasdeveloped at North Carolina State University (NCSU) with the culmination ofcommercial availability of wafers from CREE Research Corporation. Althoughdata on the impact ionization coefficients of SiC was not available, early reportson the breakdown voltage of diodes enabled estimation of the breakdown electricfield strength. Using these numbers in the BFOM predicted an impressive 100-200fold reduction in the specific on-resistance of the drift region for SiC based unipolardevices. In 1988, I joined NCSU and subsequently founded the Power Semiconduc-tor Research Center (PSRC) - an industrial consortium – with the objective ofexploring ideas to enhance power device performance. Within the first year of theinception of the program, SiC Schottky barrier rectifiers with breakdown voltage of400 volts were successfully fabricated with on-state voltage drop of about 1 volt andno reverse recovery transients [10]. By improving the edge termination of thesediodes, the breakdown voltage was found to increase to 1000 volts. With theavailability of epitaxial SiC material with lower doping concentrations, SiC Schottkyrectifiers with breakdown voltages over 2.5 kV have been fabricated at PSRC [11].These results have motivated many other groups around the world to develop SiCbased power rectifiers. In this regard, it has been my privilege to assist in theestablishment of national programs to fund research on silicon carbide technologyin the United States, Japan, and Switzerland-Sweden. Meanwhile, accurate measure-ments of the impact ionization coefficients for 6H-SiC and 4H-SiC in defect freeregions were performed at PSRC using an electron beam excitation method [12].

Preface to the First Edition xiii

Using these coefficients, a BFOM of over 1000 is predicted for SiC providing evengreater motivation to develop power devices from this material.

Although the fabrication of high performance, high voltage Schottky rectifiershas been relatively straight-forward, the development of a suitable silicon carbideMOSFET structure has been problematic. The existing silicon power D-MOSFETand U-MOSFET structures do not directly translate to suitable structures in siliconcarbide. The interface between SiC and silicon dioxide, as a gate dielectric, neededextensive investigation due to the large density of traps that prevent the formation ofhigh conductivity inversion layers. Even after overcoming this hurdle, the muchhigher electric field in the silicon dioxide when compared with silicon devices,resulting from the much larger electric field in the underlying SiC, leads to reliabilityproblems. Fortunately, a structural innovation called the ACCUFET, to overcomeboth of these problems, was proposed and demonstrated at PSRC [13]. In thisstructure, a buried P+ region is used to shield the gate region from the high electricfield within the SiC drift region. This concept is applicable to devices that utilizeeither accumulation channels or inversion channels. Devices with low specificon-resistance have been demonstrated at PSRC using both 6H-SiC and 4H-SiCwith epitaxial material capable of supporting over 5000 volts [14]. This devicestructure has been subsequently emulated by several groups around the world.

The availability of power semiconductor devices with high input impedance hasencouraged the development of integrated control circuits. In general, the integrationof the control circuit is preferred over the discrete counterpart due to reducedmanufacturing costs at high volumes and improved reliability from a reduction ofthe interconnects. Since the complexity of including additional circuitry to an IC isrelatively small, the incorporation of protective features such as over-temperature,over-current, and over-voltage has become cost effective. In addition, the chips cancontain encode/decode CMOS circuitry to interface with a central microprocessor orcomputer in the system for control and diagnostic purposes. This technology iscommonly referred to as Smart Power Technology [15].

The advent of smart power technology portends a Second Electronic Revolution.In contrast with integrated circuits for information processing, this technologyenables efficient control of power and energy. These technologies can therefore beregarded as complementary, similar to the brain and muscles in the human body.Smart power technology is having an enormous impact on society. The widespreaduse of power semiconductor devices in consumer, industrial, transportation, andmedical applications brings greater mobility and comfort to billions of people aroundthe world. Our ability to improve the efficiency for the control of electric powerresults in the conservation of fossil fuels, which in turn provides reduction ofenvironmental pollution.

Due to these developments, it is anticipated that there will be an increasing needfor technologists trained in the discipline of designing and manufacturing powersemiconductor devices. This textbook provides the knowledge in a tutorial formatsuitable for self-study or in a graduate/senior level university course. In comparisonwith my previous textbooks [16, 17] (which have gone out of print), this bookprovides a more detailed description of the operating physics of power devices.

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Analytical expressions have been rigorously derived using the fundamental semi-conductor Poisson’s, continuity, and conduction equations. The electrical character-istics of all the power devices discussed in this book can be computed using theseanalytical solutions as shown by typical examples provided in each section. Due toincreasing interest in the utilization of wide band-gap semiconductors for powerdevices, the book includes the analysis of silicon carbide structures. In order tocorroborate the validity of the analytical formulations, I have included the results oftwo-dimensional numerical simulations using MEDICI [18] in each section of thebook. The simulation results are also used to further elucidate the physics and pointout two-dimensional effects whenever relevant.

In the first chapter, a broad introduction to potential applications for powerdevices is provided. The electrical characteristics for ideal power rectifiers andtransistors are then defined and compared with those for typical devices. The secondchapter provides the transport properties of silicon and silicon carbide that haverelevance to the analysis and performance of power device structures. The thirdchapter discusses breakdown voltage, which is the most unique distinguishingcharacteristic for power devices, together with edge termination structures. Thisanalysis is pertinent to all the device structures discussed in subsequent chapters ofthe book.

The fourth chapter provides a detailed analysis of the Schottky rectifier structure.On-state current flow via thermionic emission is described followed by the impact ofimage force barrier lowering on the reverse leakage current. These phenomenainfluence the selection of the barrier height to optimize the power losses as describedin the chapter. The influence of the tunneling current component is also included inthis chapter due to its importance for silicon carbide Schottky rectifiers.

The fifth chapter describes the physics of operation of high voltage P-i-Nrectifiers. The theory for both low-level and high-level injection conditions duringon-state current flow is developed in detail. The impact of this on the reverserecovery phenomenon during turn-off is then analyzed. The influence of end regionrecombination, carrier-carrier scattering, and auger recombination are included in theanalysis.

In chapter six, an extensive discussion of the operating principles and designconsiderations is provided for the power Metal-Oxide-Semiconductor Field EffectTransistor (MOSFET) structure. The influence of the parasitic bipolar transistor onthe blocking voltage is described together with methods for its suppression. Thebasic physics of creating channels in the MOSFET structure is then developed. Theconcepts of threshold voltage, transconductance, and specific on-resistance aredescribed. The various components of the on-state resistance are analyzed andoptimization procedures are provided. Both the commercially available DMOSand UMOS structures are analyzed here. The modification of the physics requiredto produce a super-linear transfer characteristic is included due to its relevance forRF and audio applications. A detailed analysis of the device capacitances is thenprovided for use in the analysis of the switching behavior. Analysis of the gatecharge is included here because of its common use in comparing device designs. Theswitching characteristics of the power MOSFET are then related to its capacitance,

Preface to the First Edition xv

including the impact of the Miller effect. This is followed by discussion of the safe-operating-area, the integral body diode, high temperature characteristics, and com-plementary (p-channel) devices. A brief description of the process flow for theD-MOSFET and U-MOSFET structures is given in the chapter for completeness.The last portion of the chapter focuses on silicon carbide technology with the optionsof the Baliga-Pair configuration, the shielded planar structure, and the shieldedtrench-gate structure described in detail.

The seventh chapter is devoted to bipolar power transistors. The basic theory forcurrent transport and gain in an N-P-N transistor is first developed followed by adiscussion of issues relevant to power transistors. The various breakdown modes ofthe bipolar transistors are then explained. The physics governing the current gain ofthe bipolar transistor is extensively analyzed including high-level injection effects,the current-induced base, and emitter current crowding. The output characteristicsfor the bipolar transistor are then described with analysis of the saturation region, thequasi-saturation mode, and the output resistance. This is followed by analysis of theswitching characteristics. The influence of stored charge on the switching behaviorof the bipolar transistor is described in detail during both the turn-on and turn-offtransients. Issues dealing with second breakdown are then considered followed byways to improve the current gain by using the Darlington configuration.

The physics of operation of the power thyristor is considered in chapter eight. Theimpact of the four layer structure on the forward and reverse blocking capability isfirst analyzed including the use of cathode shorts. The on-state characteristics for thethyristor are then shown to approach those for a P-i-N rectifier. The gate triggeringand holding currents are related to the cathode short design. Under switchingcharacteristics, the turn-on physics is discussed with description of the involutedesign, the amplifying gate, and light-activated gate structures. The commutatedswitching behavior is also analyzed together with a discussion of voltage transients.The basic principles of the Gate Turn-Off (GTO) thyristor are then described withanalytical models for the storage, voltage-rise and current-fall times. The chapterconcludes with the description of triacs, which are commonly used for AC powercontrol.

The insulated gate bipolar transistor (IGBT) is discussed in depth in chapter nine.The benefits of controlling bipolar current transport in a wide base P-N-P transistorusing an MOS channel are explained. The design of both reverse blocking (Sym-metric) and unidirectional blocking (Asymmetric) structures are considered here.The on-state characteristics of the IGBT are then extensively analyzed including theimpact of high-level injection in the wide-base region and the finite injectionefficiency of the collector junction. The discussion includes not only the basicsymmetric IGBT structure but also the asymmetric structure and the transparentemitter structure. The utilization of lifetime control is compared with changes to theN-buffer-layer and P+ collector doping concentrations. After developing the currentsaturation model for the IGBT structure, the output characteristics for the three typesof IGBT structure are derived. The impact of the stored charge on the switchingbehavior of the device is then analyzed for the case of no-load, resistive-load, andinductive-load conditions for each of the three types of structures. The optimization

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of the power losses in the IGBT structure is then performed allowing comparison ofthe three types of structures. The next section of the chapter describes the comple-mentary (p-channel) IGBT structure. This is followed by an extensive discussion ofmethods for suppression of the parasitic thyristor in the IGBT due to its importancefor designing stable devices. The next section on the safe-operating-area includesanalysis of the FBSOA, RBSOA, and SCSOA. The trench-gate IGBT structure isthen demonstrated to produce lower on-state voltage drop. This is followed bydiscussion of scaling up the voltage rating for the IGBT and its excellent character-istics for high ambient temperatures. Various methods for improving the switchingspeed of the IGBT structure and optimizing its cell structure are then discussed. Thechapter concludes with the description of the reverse conducting IGBT structure.

The final chapter provides the basis for the comparison of various power devicesfrom an application’s viewpoint. A typical motor drive case is selected to demon-strate the reduction of power losses by optimization of the on-state and switchingcharacteristics of the devices. The importance of reducing the reverse recoverycurrent in power rectifiers is highlighted here.

Throughout the book, emphasis is placed on deriving simple analytical expres-sions that describe the underlying physics and enable representation of the deviceelectrical characteristics. This treatment is invaluable for teaching a course on powerdevices because it allows the operating principles and concepts to be conveyed withquantitative analysis. The analytical approach used in the book based on physicalinsight will provide a good foundation for the reader. The results of two dimensionalnumerical simulations have been included to supplement and reinforce the concepts.Due to space limitations, only the basic power device structures have been includedin this book. Advanced structures will be covered in monographs to be subsequentlypublished. I am hopeful that this book will be widely used for the teaching of courseson solid state devices and that it will become an essential reference for the powerdevice industry well into the future.

Raleigh, NC, USA B. Jayant BaligaDecember 2007

References

1. Baliga BJ, Ghandhi SK (1974) Heteroepitaxial InAs grown on GaAs from triethylindium andarsine. J Electrochem Soc 121:1642–1650.

2. Baliga BJ, Ghandhi SK (1975) Growth and properties of heteroepitaxial GaInAs alloys Grownon GaAs substrates from trimethylgallium, triethylindium and arsine. J Electrochem Soc122:683–687.

3. Baliga BJ, Ghandhi SK (1976) The preparation and properties of tin oxide films formed by theoxidation of trimethytin. J Electrochem Soc 123:941–944.

4. Baliga BJ, Ghandhi SK (1981) Preparation and properties of zinc oxide films grown by theoxidation of diethylzinc. J Electrochem Soc 128:558–561.

5. Baliga BJ et al. (1987) Defect levels controlling the behavior of neutron transmutation dopedsilicon during annealing. NTD Conference.

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6. Baliga BJ (1988) Evolution of MOS-bipolar power semiconductor technology. ProceedingsIEEE. pp. 409–418.

7. Baliga BJ et al. (981) Breakdown characteristics of gallium arsenide. IEEE Electron DeviceLetters EDL-2:302–304.

8. Baliga BJ, Garwacki W, Walden JP (1985) Gallium Arsenide Schottky Power Rectifiers. IEEETransact Electr Dev ED-32:1130–1134.

9. Campbell PM et al. (1985) Trapezoidal-Groove Schottky-Gate vertical-channel GaAs FET.IEEE Electr Device Lett EDL-6:304–306.

10. Bhatnagar M, McLarty PK, Baliga BJ (1992) Silicon-carbide high-voltage (400 V) Schottkybarrier diodes. IEEE Elect Device Lett EDL-13:501–503.

11. Chilukuri RK, Baliga BJ (1999) High voltage Ni/4H-SiC Schottky rectifiers. Internationalsymposium on power semiconductor devices and ICs. pp. 161–164.

12. Raghunathan R, Baliga BJ. Temperature dependence of hole impact ionization coefficients in4H and 6H-SiC. Solid State Electron 43:199–211.

13. Shenoy PM, Baliga BJ (1997) High voltage planar 6H-SiC ACCUFET. International Confer-ence on Silicon Carbide, III-Nitrides, and Related Materials, Abstract Tu3b-3. pp. 158–159.

14. Chilukuri RK, Baliga BJ (2000) PSRC Technical Report TR-00-007.15. Baliga BJ (1990) Smart power technology: an elephantine opportunity. Invited Plenary Talk,

IEEE International Electron Devices Meeting, pp. 3–6.16. Baliga BJ (1987) Modern power devices. John Wiley and Sons.17. Baliga BJ (1996) Power semiconductor devices. PWS Publishing Company.18. MEDICI TCAD Simulator, Avanti Corporation, Fremont, CA 94538.

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Contents

1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.1 Ideal and Typical Power-Switching Waveforms . . . . . . . . . . . . . 31.2 Ideal and Typical Power Device Characteristics . . . . . . . . . . . . . 51.3 Unipolar Power Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81.4 Bipolar Power Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101.5 MOS-Bipolar Power Devices . . . . . . . . . . . . . . . . . . . . . . . . . . 101.6 Ideal Drift Region for Unipolar Power Devices . . . . . . . . . . . . . 141.7 Charge-Coupled Structures: Ideal Specific On-Resistance . . . . . . 161.8 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

2 Material Properties and Transport Physics . . . . . . . . . . . . . . . . . . 232.1 Fundamental Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

2.1.1 Intrinsic Carrier Concentration . . . . . . . . . . . . . . . . . . . 242.1.2 Bandgap Narrowing . . . . . . . . . . . . . . . . . . . . . . . . . . 262.1.3 Built-in Potential . . . . . . . . . . . . . . . . . . . . . . . . . . . . 302.1.4 Zero-Bias Depletion Width . . . . . . . . . . . . . . . . . . . . . 322.1.5 Impact Ionization Coefficients . . . . . . . . . . . . . . . . . . . 322.1.6 Carrier Mobility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

2.2 Resistivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 512.2.1 Intrinsic Resistivity . . . . . . . . . . . . . . . . . . . . . . . . . . . 512.2.2 Extrinsic Resistivity . . . . . . . . . . . . . . . . . . . . . . . . . . 512.2.3 Neutron Transmutation Doping . . . . . . . . . . . . . . . . . . 54

2.3 Recombination Lifetime . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 592.3.1 Shockley-Read-Hall Recombination . . . . . . . . . . . . . . . 602.3.2 Low-Level Lifetime . . . . . . . . . . . . . . . . . . . . . . . . . . 632.3.3 Space-Charge Generation Lifetime . . . . . . . . . . . . . . . . 642.3.4 Recombination Level Optimization . . . . . . . . . . . . . . . 66

xix

2.3.5 Lifetime Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 752.3.6 Auger Recombination . . . . . . . . . . . . . . . . . . . . . . . . . 80

2.4 Ohmic Contacts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 822.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85

3 Breakdown Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 893.1 Avalanche Breakdown . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90

3.1.1 Power Law Approximations for the ImpactIonization Coefficients . . . . . . . . . . . . . . . . . . . . . . . . 90

3.1.2 Multiplication Coefficient . . . . . . . . . . . . . . . . . . . . . 923.2 Abrupt One-Dimensional Diode . . . . . . . . . . . . . . . . . . . . . . . 94

3.2.1 Temperature Dependence . . . . . . . . . . . . . . . . . . . . . 993.3 Ideal Specific On-Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . 993.4 Abrupt Punch-Through Diode . . . . . . . . . . . . . . . . . . . . . . . . . 1003.5 Linearly Graded Junction Diode . . . . . . . . . . . . . . . . . . . . . . . 1023.6 Edge Terminations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106

3.6.1 Planar Junction Termination . . . . . . . . . . . . . . . . . . . 1063.6.2 Planar Junction with Floating Field Ring . . . . . . . . . . 1193.6.3 Planar Junction with Multiple Floating Field

Rings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1293.6.4 Planar Junction with Field Plate . . . . . . . . . . . . . . . . . 1313.6.5 Planar Junction with Field Plates and Field

Rings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1363.6.6 Bevel Edge Terminations . . . . . . . . . . . . . . . . . . . . . . 1363.6.7 Etch Terminations . . . . . . . . . . . . . . . . . . . . . . . . . . . 1473.6.8 Junction Termination Extension . . . . . . . . . . . . . . . . . 148

3.7 Open-Base Transistor Breakdown . . . . . . . . . . . . . . . . . . . . . . 1533.7.1 Composite Bevel Termination . . . . . . . . . . . . . . . . . . 1583.7.2 Double-Positive Bevel Termination . . . . . . . . . . . . . . 159

3.8 Surface Passivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1613.9 Silicon Carbide Edge Terminations . . . . . . . . . . . . . . . . . . . . . 162

3.9.1 Argon-Implanted Edge Termination . . . . . . . . . . . . . . 1623.9.2 Multiple-Floating-Zone Junction Termination

Extension . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1633.9.3 Hybrid Junction Termination Extension . . . . . . . . . . . 1633.9.4 Multiple Floating Field Ring Design . . . . . . . . . . . . . 1643.9.5 Orthogonal Positive Bevel Termination . . . . . . . . . . . 166

3.10 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168

4 Schottky Rectifiers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1714.1 Power Schottky Rectifier Structure . . . . . . . . . . . . . . . . . . . . . 1724.2 Metal-Semiconductor Contact . . . . . . . . . . . . . . . . . . . . . . . . . 1734.3 Forward Conduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175

xx Contents

4.4 Reverse Blocking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1834.4.1 Leakage Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1844.4.2 Schottky Barrier Lowering . . . . . . . . . . . . . . . . . . . . . 1854.4.3 Pre-breakdown Avalanche Multiplication . . . . . . . . . . 1884.4.4 Silicon Carbide Rectifiers . . . . . . . . . . . . . . . . . . . . . 189

4.5 Device Capacitance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1914.6 Thermal Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1924.7 Fundamental Trade-Off Analysis . . . . . . . . . . . . . . . . . . . . . . 1964.8 Device Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1984.9 Barrier Height Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . 1994.10 Edge Terminations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2014.11 Reverse Recovery Current . . . . . . . . . . . . . . . . . . . . . . . . . . . 2024.12 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206

5 P-i-N Rectifiers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2075.1 One-Dimensional Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . 208

5.1.1 Recombination Current . . . . . . . . . . . . . . . . . . . . . . . 2095.1.2 Low-Level Injection Current . . . . . . . . . . . . . . . . . . . 2105.1.3 High-Level Injection Current . . . . . . . . . . . . . . . . . . . 2125.1.4 Injection into the End Regions . . . . . . . . . . . . . . . . . . 2215.1.5 Carrier-Carrier Scattering Effect . . . . . . . . . . . . . . . . . 2235.1.6 Auger Recombination Effect . . . . . . . . . . . . . . . . . . . 2235.1.7 Forward Conduction Characteristics . . . . . . . . . . . . . . 225

5.2 Silicon Carbide P-i-N Rectifiers . . . . . . . . . . . . . . . . . . . . . . . 2345.3 Reverse Blocking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2365.4 Switching Performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240

5.4.1 Forward Recovery . . . . . . . . . . . . . . . . . . . . . . . . . . . 2405.4.2 Reverse Recovery . . . . . . . . . . . . . . . . . . . . . . . . . . . 247

5.5 P-i-N Rectifier Structure with Buffer Layer . . . . . . . . . . . . . . . 2655.6 Non-Punch-Through P-i-N Rectifier Structure . . . . . . . . . . . . . 2665.7 P-i-N Rectifier Trade-Off Curves . . . . . . . . . . . . . . . . . . . . . . 273

5.7.1 Lifetime Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2765.8 Safe Operating Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2775.9 Maximum Allowable [dJ/dt] . . . . . . . . . . . . . . . . . . . . . . . . . . 2795.10 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 280References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 281

6 Power MOSFETs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2836.1 Ideal Specific On-Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . 2846.2 Device Cell Structure and Operation . . . . . . . . . . . . . . . . . . . . 286

6.2.1 The V-MOSFET Structure . . . . . . . . . . . . . . . . . . . . . 2876.2.2 The VD-MOSFET Structure . . . . . . . . . . . . . . . . . . . 2886.2.3 The U-MOSFET Structure . . . . . . . . . . . . . . . . . . . . . 289

6.3 Basic Device Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . 291

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6.4 Blocking Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2936.4.1 Impact of Edge Termination . . . . . . . . . . . . . . . . . . . 2946.4.2 Impact of Graded Doping Profile . . . . . . . . . . . . . . . . 2956.4.3 Impact of Parasitic Bipolar Transistor . . . . . . . . . . . . . 2966.4.4 Impact of Cell Pitch . . . . . . . . . . . . . . . . . . . . . . . . . 2976.4.5 Impact of Gate Shape . . . . . . . . . . . . . . . . . . . . . . . . 3006.4.6 Impact of Cell Surface Topology . . . . . . . . . . . . . . . . 303

6.5 Forward Conduction Characteristics . . . . . . . . . . . . . . . . . . . . 3056.5.1 MOS Interface Physics . . . . . . . . . . . . . . . . . . . . . . . 3056.5.2 MOS Surface Charge Analysis . . . . . . . . . . . . . . . . . . 3096.5.3 Maximum Depletion Width . . . . . . . . . . . . . . . . . . . . 3146.5.4 Threshold Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . 3166.5.5 Channel Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . 326

6.6 Power VD-MOSFET On-Resistance . . . . . . . . . . . . . . . . . . . . 3316.6.1 Source Contact Resistance . . . . . . . . . . . . . . . . . . . . . 3346.6.2 Source Region Resistance . . . . . . . . . . . . . . . . . . . . . 3356.6.3 Channel Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . 3366.6.4 Accumulation Resistance . . . . . . . . . . . . . . . . . . . . . . 3376.6.5 JFET Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3386.6.6 Drift Region Resistance . . . . . . . . . . . . . . . . . . . . . . . 3396.6.7 N+ Substrate Resistance . . . . . . . . . . . . . . . . . . . . . . . 3446.6.8 Drain Contact Resistance . . . . . . . . . . . . . . . . . . . . . . 3446.6.9 Total On-Resistance . . . . . . . . . . . . . . . . . . . . . . . . . 345

6.7 Power VD-MOSFET Cell Optimization . . . . . . . . . . . . . . . . . 3486.7.1 Optimization of Gate Electrode Width . . . . . . . . . . . . 3486.7.2 Impact of Breakdown Voltage . . . . . . . . . . . . . . . . . . 3506.7.3 Impact of Design Rules . . . . . . . . . . . . . . . . . . . . . . . 3536.7.4 Impact of Cell Topology . . . . . . . . . . . . . . . . . . . . . . 355

6.8 Power U-MOSFET On-Resistance . . . . . . . . . . . . . . . . . . . . . 3636.8.1 Source Contact Resistance . . . . . . . . . . . . . . . . . . . . . 3646.8.2 Source Region Resistance . . . . . . . . . . . . . . . . . . . . . 3666.8.3 Channel Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . 3666.8.4 Accumulation Resistance . . . . . . . . . . . . . . . . . . . . . . 3676.8.5 Drift Region Resistance . . . . . . . . . . . . . . . . . . . . . . . 3686.8.6 N+ Substrate Resistance . . . . . . . . . . . . . . . . . . . . . . . 3706.8.7 Drain Contact Resistance . . . . . . . . . . . . . . . . . . . . . . 3706.8.8 Total On-Resistance . . . . . . . . . . . . . . . . . . . . . . . . . 370

6.9 Power U-MOSFET Cell Optimization . . . . . . . . . . . . . . . . . . . 3736.9.1 Orthogonal P-Base Contact Structure . . . . . . . . . . . . . 3736.9.2 Impact of Breakdown Voltage . . . . . . . . . . . . . . . . . . 3756.9.3 Ruggedness Improvement . . . . . . . . . . . . . . . . . . . . . 377

6.10 Square-Law Transfer Characteristics . . . . . . . . . . . . . . . . . . . . 3786.11 Superlinear Transfer Characteristics . . . . . . . . . . . . . . . . . . . . 3826.12 Output Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 387

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6.13 Device Capacitances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3916.13.1 Basic MOS Capacitance . . . . . . . . . . . . . . . . . . . . . . 3916.13.2 Power VD-MOSFET Structure Capacitances . . . . . . . . 3946.13.3 Power U-MOSFET Structure Capacitances . . . . . . . . . 4036.13.4 Equivalent Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . 413

6.14 Gate Charge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4146.14.1 Charge Extraction . . . . . . . . . . . . . . . . . . . . . . . . . . . 4156.14.2 Voltage and Current Dependence . . . . . . . . . . . . . . . . 4226.14.3 VD-MOSFET Versus U-MOSFET Structure . . . . . . . . 4256.14.4 Impact of VD-MOSFET and U-MOSFET

Cell Pitch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4286.15 Optimization for High-Frequency Operation . . . . . . . . . . . . . . 432

6.15.1 Input Switching Power Loss . . . . . . . . . . . . . . . . . . . 4326.15.2 Output Switching Power Loss . . . . . . . . . . . . . . . . . . 4386.15.3 Gate Propagation Delay . . . . . . . . . . . . . . . . . . . . . . . 440

6.16 Switching Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4416.16.1 Turn-On Transient . . . . . . . . . . . . . . . . . . . . . . . . . . 4436.16.2 Turn-Off Transient . . . . . . . . . . . . . . . . . . . . . . . . . . 4466.16.3 Switching Power Losses . . . . . . . . . . . . . . . . . . . . . . 4486.16.4 [dV/dt] Capability . . . . . . . . . . . . . . . . . . . . . . . . . . . 449

6.17 Safe Operating Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4536.17.1 Bipolar Second Breakdown . . . . . . . . . . . . . . . . . . . . 4556.17.2 MOS Second Breakdown . . . . . . . . . . . . . . . . . . . . . 457

6.18 Integral Body Diode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4586.18.1 Reverse Recovery Enhancement . . . . . . . . . . . . . . . . 4596.18.2 Impact of Parasitic Bipolar Transistor . . . . . . . . . . . . . 460

6.19 High-Temperature Characteristics . . . . . . . . . . . . . . . . . . . . . . 4606.19.1 Threshold Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . 4616.19.2 On-Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4626.19.3 Saturation Transconductance . . . . . . . . . . . . . . . . . . . 463

6.20 Complementary Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4646.20.1 P-channel Structure . . . . . . . . . . . . . . . . . . . . . . . . . . 4646.20.2 On-Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4656.20.3 Deep-Trench Structure . . . . . . . . . . . . . . . . . . . . . . . 465

6.21 Silicon Power MOSFET Process Technology . . . . . . . . . . . . . 4666.21.1 Planar VD-MOSFET Process . . . . . . . . . . . . . . . . . . . 4666.21.2 Trench U-MOSFET Process . . . . . . . . . . . . . . . . . . . 469

6.22 Silicon Carbide Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4716.22.1 The Baliga-Pair Configuration . . . . . . . . . . . . . . . . . . 4716.22.2 Planar Power MOSFET Structure . . . . . . . . . . . . . . . . 4826.22.3 Shielded Planar Power MOSFET Structures . . . . . . . . 4886.22.4 Shielded Trench-Gate Power MOSFET Structure . . . . 4966.22.5 JBSFET Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . 5066.22.6 Bidirectional Field-Effect Transistor . . . . . . . . . . . . . . 507

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6.23 Unclamped Inductive Load Turn-Off . . . . . . . . . . . . . . . . . . . 5116.24 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 514References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 518

7 Bipolar Junction Transistors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5217.1 Power Bipolar Junction Transistor Structure . . . . . . . . . . . . . . 5227.2 Basic Operating Principles . . . . . . . . . . . . . . . . . . . . . . . . . . . 5247.3 Static Blocking Characteristics . . . . . . . . . . . . . . . . . . . . . . . . 527

7.3.1 Open-Emitter Breakdown Voltage . . . . . . . . . . . . . . . 5277.3.2 Open-Base Breakdown Voltage . . . . . . . . . . . . . . . . . 5287.3.3 Shorted Base-Emitter Operation . . . . . . . . . . . . . . . . . 530

7.4 Current Gain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5337.4.1 Emitter Injection Efficiency . . . . . . . . . . . . . . . . . . . . 5367.4.2 Emitter Injection Efficiency with Recombination

in the Depletion Region . . . . . . . . . . . . . . . . . . . . . . . 5407.4.3 Emitter Injection Efficiency with High-Level

Injection in the Base . . . . . . . . . . . . . . . . . . . . . . . . . 5417.4.4 Base Transport Factor . . . . . . . . . . . . . . . . . . . . . . . . 5477.4.5 Base Widening at High Collector Current Density . . . . 550

7.5 Emitter Current Crowding . . . . . . . . . . . . . . . . . . . . . . . . . . . 5647.5.1 Low-Level Injection in the Base . . . . . . . . . . . . . . . . . 5657.5.2 High-Level Injection in the Base . . . . . . . . . . . . . . . . 5697.5.3 Emitter Geometry . . . . . . . . . . . . . . . . . . . . . . . . . . . 573

7.6 Output Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5747.7 On-State Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 579

7.7.1 Saturation Region . . . . . . . . . . . . . . . . . . . . . . . . . . . 5817.7.2 Quasi-Saturation Region . . . . . . . . . . . . . . . . . . . . . . 585

7.8 Switching Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5897.8.1 Turn-On Transition . . . . . . . . . . . . . . . . . . . . . . . . . . 5897.8.2 Turn-Off Transition . . . . . . . . . . . . . . . . . . . . . . . . . . 601

7.9 Safe Operating Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6247.9.1 Forward Biased Second Breakdown . . . . . . . . . . . . . . 6257.9.2 Reverse Biased Second Breakdown . . . . . . . . . . . . . . 6287.9.3 Boundary for Safe Operating Area . . . . . . . . . . . . . . . 632

7.10 Darlington Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6337.11 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 636References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 638

8 Thyristors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6418.1 Power Thyristor Structure and Operation . . . . . . . . . . . . . . . . . 6448.2 Blocking Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 648

8.2.1 Reverse Blocking Capability . . . . . . . . . . . . . . . . . . . 6488.2.2 Forward Blocking Capability . . . . . . . . . . . . . . . . . . . 6528.2.3 Cathode Shorting . . . . . . . . . . . . . . . . . . . . . . . . . . . 6578.2.4 Cathode Shorting Geometry . . . . . . . . . . . . . . . . . . . . 660

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8.3 On-State Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6678.3.1 On-State Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 6698.3.2 Gate Triggering Current . . . . . . . . . . . . . . . . . . . . . . 6718.3.3 Holding Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . 674

8.4 Switching Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6798.4.1 Turn-On Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6798.4.2 Gate Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6888.4.3 Amplifying Gate Design . . . . . . . . . . . . . . . . . . . . . . 6898.4.4 [dV/dt] Capability . . . . . . . . . . . . . . . . . . . . . . . . . . . 6928.4.5 Turn-Off Process . . . . . . . . . . . . . . . . . . . . . . . . . . . 699

8.5 Light-Activated Thyristors . . . . . . . . . . . . . . . . . . . . . . . . . . . 7028.5.1 [dI/dt] Capability . . . . . . . . . . . . . . . . . . . . . . . . . . . 7028.5.2 Gate Region Design . . . . . . . . . . . . . . . . . . . . . . . . . 7048.5.3 Optically Generated Current Density . . . . . . . . . . . . . 7058.5.4 Amplifying Gate Design . . . . . . . . . . . . . . . . . . . . . . 706

8.6 Self-Protected Thyristors . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7078.6.1 Forward Breakdown Protection . . . . . . . . . . . . . . . . . 7078.6.2 [dV/dt] Turn-On Protection . . . . . . . . . . . . . . . . . . . . 711

8.7 The Gate Turn-Off Thyristor Structure . . . . . . . . . . . . . . . . . . 7148.7.1 Basic Structure and Operation . . . . . . . . . . . . . . . . . . 7158.7.2 One-Dimensional Turn-Off Criterion . . . . . . . . . . . . . 7188.7.3 One-Dimensional Storage Time Analysis . . . . . . . . . . 7208.7.4 Two-Dimensional Storage Time Model . . . . . . . . . . . 7208.7.5 One-Dimensional Voltage Rise-Time Model . . . . . . . . 7228.7.6 One-Dimensional Current Fall-Time Model . . . . . . . . 7258.7.7 Switching Energy Loss . . . . . . . . . . . . . . . . . . . . . . . 7378.7.8 Maximum Turn-Off Current . . . . . . . . . . . . . . . . . . . 7398.7.9 Cell Design and Layout . . . . . . . . . . . . . . . . . . . . . . . 741

8.8 The Triac Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7438.8.1 Basic Structure and Operation . . . . . . . . . . . . . . . . . . 7448.8.2 Gate Triggering Mode 1 . . . . . . . . . . . . . . . . . . . . . . 7478.8.3 Gate Triggering Mode 2 . . . . . . . . . . . . . . . . . . . . . . 7478.8.4 [dV/dt] Capability . . . . . . . . . . . . . . . . . . . . . . . . . . . 748

8.9 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 749References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 752

9 Insulated Gate Bipolar Transistors . . . . . . . . . . . . . . . . . . . . . . . . 7559.1 Basic Device Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7599.2 Device Operation and Output Characteristics . . . . . . . . . . . . . . 7639.3 Device Equivalent Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . 7659.4 Blocking Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 766

9.4.1 Symmetric Structure Forward BlockingCapability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 767

9.4.2 Symmetric Structure Reverse BlockingCapability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 770

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9.4.3 Symmetric Structure Leakage Current . . . . . . . . . . . . 7729.4.4 Asymmetric Structure Forward Blocking

Capability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7789.4.5 Asymmetric Structure Reverse Blocking

Capability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7859.4.6 Asymmetric Structure Leakage Current . . . . . . . . . . . 787

9.5 On-State Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7949.5.1 On-State Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7959.5.2 On-State Carrier Distribution: Symmetric

Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8029.5.3 On-State Voltage Drop: Symmetric Structure . . . . . . . 8099.5.4 On-State Carrier Distribution: Asymmetric

Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8139.5.5 On-State Voltage Drop: Asymmetric Structure . . . . . . 8209.5.6 On-State Carrier Distribution: Transparent Emitter

Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8259.5.7 On-State Voltage Drop: Transparent Emitter

Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8319.6 Current Saturation Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . 833

9.6.1 Carrier Distribution: Symmetric Structure . . . . . . . . . . 8389.6.2 Output Characteristics: Symmetric Structure . . . . . . . . 8469.6.3 Output Resistance: Symmetric Structure . . . . . . . . . . . 8519.6.4 Carrier Distribution: Asymmetric Structure . . . . . . . . . 8529.6.5 Output Characteristics: Asymmetric Structure . . . . . . . 8629.6.6 Output Resistance: Asymmetric Structure . . . . . . . . . . 8669.6.7 Carrier Distribution: Transparent Emitter Structure . . . 8679.6.8 Output Characteristics: Transparent Emitter

Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8709.6.9 Output Resistance: Transparent Emitter Structure . . . . 874

9.7 Switching Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8749.7.1 Turn-On Physics: Forward Recovery . . . . . . . . . . . . . 8769.7.2 Turn-Off Physics: No-Load Conditions . . . . . . . . . . . 8839.7.3 Turn-Off Physics: Resistive Load . . . . . . . . . . . . . . . . 8859.7.4 Turn-Off Physics: Inductive Load . . . . . . . . . . . . . . . 8949.7.5 Energy Loss per Cycle . . . . . . . . . . . . . . . . . . . . . . . 922

9.8 Power-Loss Optimization . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9259.8.1 Symmetric Structure . . . . . . . . . . . . . . . . . . . . . . . . . 9259.8.2 Asymmetric Structure . . . . . . . . . . . . . . . . . . . . . . . . 9279.8.3 Transparent Emitter Structure . . . . . . . . . . . . . . . . . . . 9289.8.4 Comparison of Trade-Off Curves . . . . . . . . . . . . . . . . 930

9.9 Complementary (p-Channel) Structure . . . . . . . . . . . . . . . . . . 9319.9.1 On-State Characteristics . . . . . . . . . . . . . . . . . . . . . . 9349.9.2 Switching Characteristics . . . . . . . . . . . . . . . . . . . . . . 9369.9.3 Power-Loss Optimization . . . . . . . . . . . . . . . . . . . . . 938

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9.10 Latch-Up Suppression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9399.10.1 Deep P+ Diffusion . . . . . . . . . . . . . . . . . . . . . . . . . . . 9409.10.2 Shallow P+ Layer . . . . . . . . . . . . . . . . . . . . . . . . . . . 9469.10.3 Reduced Gate Oxide Thickness . . . . . . . . . . . . . . . . . 9499.10.4 Bipolar Current Bypass . . . . . . . . . . . . . . . . . . . . . . . 9549.10.5 Diverter Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . 9589.10.6 Cell Topology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9609.10.7 Latch-Up Proof Structure . . . . . . . . . . . . . . . . . . . . . . 966

9.11 Safe Operating Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9699.11.1 Forward-Biased Safe Operating Area . . . . . . . . . . . . . 9709.11.2 Reverse-Biased Safe Operating Area . . . . . . . . . . . . . 9749.11.3 Short-Circuit Safe Operating Area . . . . . . . . . . . . . . . 978

9.12 Trench-Gate Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9849.12.1 Blocking Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9859.12.2 On-State Carrier Distribution . . . . . . . . . . . . . . . . . . . 9869.12.3 On-State Voltage Drop . . . . . . . . . . . . . . . . . . . . . . . 9889.12.4 Switching Characteristics . . . . . . . . . . . . . . . . . . . . . . 9909.12.5 Safe Operating Area . . . . . . . . . . . . . . . . . . . . . . . . . 9919.12.6 Modified Structures . . . . . . . . . . . . . . . . . . . . . . . . . . 996

9.13 Blocking Voltage Scaling . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9989.13.1 N-Base Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9989.13.2 Power MOSFET Baseline . . . . . . . . . . . . . . . . . . . . . 10009.13.3 On-State Characteristics . . . . . . . . . . . . . . . . . . . . . . 10009.13.4 Trade-Off Curve . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1003

9.14 High-Temperature Operation . . . . . . . . . . . . . . . . . . . . . . . . . 10049.14.1 On-State Characteristics . . . . . . . . . . . . . . . . . . . . . . 10049.14.2 Latch-Up Characteristics . . . . . . . . . . . . . . . . . . . . . . 1007

9.15 Lifetime Control Techniques . . . . . . . . . . . . . . . . . . . . . . . . . 10099.15.1 Electron Irradiation . . . . . . . . . . . . . . . . . . . . . . . . . . 10109.15.2 Neutron Irradiation . . . . . . . . . . . . . . . . . . . . . . . . . . 10119.15.3 Helium Irradiation . . . . . . . . . . . . . . . . . . . . . . . . . . . 1012

9.16 Cell Optimization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10129.16.1 Planar-Gate Structure . . . . . . . . . . . . . . . . . . . . . . . . 10139.16.2 Trench-Gate Structure . . . . . . . . . . . . . . . . . . . . . . . . 1017

9.17 Reverse Conducting Structure . . . . . . . . . . . . . . . . . . . . . . . . . 10249.18 Soft Switching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10329.19 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1036References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1041

10 Synopsis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104510.1 Typical H-Bridge Topology . . . . . . . . . . . . . . . . . . . . . . . . . . 104510.2 Power-Loss Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104710.3 Low DC-Bus Voltage Applications . . . . . . . . . . . . . . . . . . . . . 105010.4 Medium DC-Bus Voltage Applications . . . . . . . . . . . . . . . . . . 1054

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10.5 High DC-Bus Voltage Applications . . . . . . . . . . . . . . . . . . . . 105810.6 Social Impact . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106210.7 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1064References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1065

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1067

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About the Author

B. Jayant Baliga is internationally recognized for his leadership in the area ofpower semiconductor devices. In addition to over 600 publications in internationaljournals and conference digests, he has authored and edited 20 books (PowerTransistors, IEEE Press, 1984; Epitaxial Silicon Technology, Academic Press,1986;Modern Power Devices, John Wiley, 1987; High Voltage Integrated Circuits,IEEE Press, 1988; Solution Manual: Modern Power Devices, John Wiley, 1988;Proceedings of the 3rd Int. Symposium on Power Devices and ICs, IEEE Press,1991; Modern Power Devices, Krieger Publishing Co., 1992;Proceedings of the 5thInt. Symposium on Power Devices and ICs, IEEE Press, 1993; Power SemiconductorDevices; PWS Publishing Company, 1995; Solution Manual: Power SemiconductorDevices; PWS Publishing Company, 1996; Cryogenic Operation of Power Devices,Kluwer Press, 1998; Silicon RF Power MOSFETs, World Scientific PublishingCompany, 2005; Silicon Carbide Power Devices, World Scientific Publishing Com-pany, 2006; Fundamentals of Power Semiconductor Devices, Springer Science,2008; Solution Manual: Fundamentals of Power Semiconductor Devices, SpringerScience, 2008; Advanced Power Rectifier Concepts, Springer Science, 2009;Advanced Power MOSFET Concepts, Springer Science, 2010; Advanced HighVoltage Power Device Concepts, Springer Science, 2011; The IGBT Device,Elsevier Press, 2015; Gallium Nitride and Silicon Carbide Power Devices; WorldScientific Press Company, 2017). In addition, he has contributed chapters to another20 books. He holds 120 US patents in the solid-state area. In 1995, one of hisinventions was selected for the B.F. Goodrich Collegiate Inventors Award presentedat the National Inventors Hall of Fame.

Professor Baliga obtained his Bachelor of Technology degree in 1969 from theIndian Institute of Technology Madras, India. He was the recipient of the PhilipsIndia Medal and the Special Merit Medal (as Valedictorian) at IIT Madras. Heobtained his masters and Ph.D. degrees from Rensselaer Polytechnic Institute, Troy,New York, in 1971 and 1974, respectively. His thesis work involved galliumarsenide diffusion mechanisms and pioneering work on the growth of InAs and

xxix

GaInAs layers using organometallic CVD techniques. At R.P.I., he was the recipientof the IBM Fellowship in 1972 and the Allen B. DuMont Prize in 1974.

From 1974 to 1988, Dr. Baliga performed research and directed a group of40 scientists at the General Electric Research and Development Center in Schenec-tady, New York, in the area of power semiconductor devices and high voltageintegrated circuits. During this time, he pioneered the concept of MOS-bipolarfunctional integration to create a new family of discrete devices. He is the inventorof the insulated gate bipolar transistor (IGBT) which is now in production by manyinternational semiconductor companies. This invention is widely used around theglobe for air conditioning, home appliance (washing machines, refrigerators, mixers,etc.) control, factory automation (robotics), medical systems (CAT scanners,uninterruptible power supplies), and electric streetcars/bullet trains, as well as forthe drivetrain in electric and hybrid electric cars under development for reducingurban pollution. The introduction of electronic ignition systems based upon IGBTsin 1990 has produced a saving of over 1.5 trillion gallons of gasoline during the last25 years. The creation of adjustable speed drives and compact fluorescent lampsbased upon IGBTs has reduced electrical energy consumption by over 75,000terawatt hours during the past 25 years. The cumulative impact of these energysavings on the environment is a reduction in carbon dioxide emissions from coal-fired power plants by over 100 trillion pounds over the last 25 years. In recognitionof this benefit to mankind, he has been referred to as the man with the largestnegative carbon footprint in the world. Most recently, the IGBT has enabledfabrication of very compact, lightweight, and inexpensive defibrillators used toresuscitate cardiac arrest victims. When installed in fire trucks, paramedic vans,and onboard airlines, it is projected by the American Medical Association (AMA) tosave 100,000 lives per year in the United States. For this work, Scientific Americanmagazine named him one of the eight heroes of the semiconductor revolution in their1997 special issue commemorating the Solid-State Century.

Dr. Baliga is also the originator of the concept of merging Schottky and P-Njunction physics to create a new family of power rectifiers that are commerciallyavailable from various companies. In 1979, he theoretically demonstrated that theperformance of power MOSFETs could be enhanced by several orders of magnitudeby replacing silicon with other materials such as gallium arsenide and siliconcarbide. This is forming the basis of a new generation of power devices in thetwenty-first century.

In August 1988, Dr. Baliga joined the faculty of the Department of Electrical andComputer Engineering at the North Carolina State University, Raleigh, NorthCarolina, as a full professor. At NCSU, in 1991, he established an internationalcenter called the Power Semiconductor Research Center (PSRC) for research in thearea of power semiconductor devices and high-voltage integrated circuits and hasserved as its founding director. His research interests include the modeling of noveldevice concepts, device fabrication technology, and the investigation of the impactof new materials, such as GaAs and silicon carbide, on power devices. In 1997, inrecognition of his contributions to NCSU, he was given the highest universityfaculty rank of Distinguished University Professor of Electrical Engineering.

xxx About the Author

He is a founding member of the Future Renewable Electrical Energy Distributionand Management (FREEDM) Systems Center, a $50 million engineering researchcenter sponsored in 2008 by the National Science Foundation. As the post-silicondevices thrust leader, he created the 10-year roadmap for power devices at FREEDMand has been developing ultrahigh voltage (10–15 kV) silicon carbide power devicesfor utility applications.

In 2015, NCSU was awarded its largest grant, a $140 million manufacturinginstitute, called the PowerAmerica created by President Obama, based upon aproposal supported by his leadership in wide bandgap-based power devices. Hehas created the national process, called PRESiCE™ (Process Engineered formanufacturing SiC Electronic-devices), in this effort for the production of siliconcarbide power rectifiers and MOSFETs. He has also created the first SiC JBSFETsand a unique four-terminal bidirectional switch, named BiDFET, for matrix con-verter applications.

In 1999, Prof. Baliga founded a company, Giant Semiconductor Corporation,with seed investment from Centennial Venture Partners, to acquire an exclusivelicense for his patented technology from the North Carolina State University with thegoal of bringing his NCSU inventions to the marketplace. A company, Micro-OhmCorporation, subsequently formed by him in 1999, has been successful in licensingthe GD-TMBS power rectifier technology to several major semiconductor compa-nies for worldwide distribution. These devices have application in power supplies,battery chargers, and automotive electronics. In June 2000, Prof. Baliga foundedanother company, Silicon Wireless Corporation, to commercialize a novelsuperlinear silicon RF transistor that he invented for application in cellular basestations and grew it to 41 employees. This company (renamed Silicon Semiconduc-tor Corporation) is located at Research Triangle Park, North Carolina. It received aninvestment of $10 million from Fairchild Semiconductor Corporation in December2000 to codevelop and market this technology. Based upon his additional inven-tions, this company has also produced a new generation of power MOSFETs fordelivering power to microprocessors in notebooks and servers. This technology waslicensed by his company to Linear Technologies Corporation with transfer of theknow-how and manufacturing process. Voltage regulator modules (VRMs) using histransistors are currently available in the market for powering microprocessor andgraphic chips in laptops and servers.

Professor Baliga has received numerous awards in recognition for his contribu-tions to semiconductor devices. These include two IR 100 awards (1983, 1984), theDushman and Coolidge Awards at GE (1983), and being selected among the 100Brightest Young Scientists in America by Science Digest magazine (1984). In 1984,he was given the Applied Sciences Award by the world-famous sitar maestro RaviShankar at the Third Convention of Asians in North America. In 1992, he was thefirst recipient of the BSS Society’s Pride of India Award. At the age of 45, he waselected as the foreign affiliate to the prestigious National Academy of Engineeringand was one of the only four citizens of India to have the honor at that time(converted to regular member in 2000 after taking US citizenship). In 1998, theUniversity of North Carolina system selected him for the O. Max Gardner Award,

About the Author xxxi

which recognizes the faculty member among the 16 constituent universities who hasmade the greatest contribution to the welfare of the human race. In April 2000, hewas honored by his alma mater as a Distinguished Alumnus. In November 2000, hereceived the R.J. Reynolds Tobacco Company Award for Excellence in Teaching,Research, and Extension for his contributions to the College of Engineering at theNorth Carolina State University.

He was elected Fellow of the IEEE in 1983 at the age of 35 for his contributions topower semiconductor devices. He received the 1991 IEEE William E. Newell PowerElectronics Award, the highest honor given by the Power Electronics Society,followed by the 1993 IEEE Morris E. Liebman Award for his contributions to theemerging smart power technology. In December 1998, he received the J.J. EbersAward, the highest recognition given by the IEEE Electron Devices Society for histechnical contributions to the solid-state area. In June 1999, he was honored at thePalace of Whitehall in London with the IEEE Lamme Medal, one of the highestforms of recognition given by the IEEE Board of Governors, for his contributions tothe development of an apparatus/technology of benefit to the society. He was giventhe highest IEEE award, the IEEE Medal of Honor, by the IEEE Board of Governorsin 2014 for his contributions to the electrical and electronics field. In 2015, he wasdeclared a Celebrated Member by the IEEE Electron Devices Society, among onlysix legendary individuals.

In 2011, he received the National Medal of Technology and Innovation fromPresident Obama at the White House, the highest honor accorded to an engineer bythe US Government. He received the North Carolina Award for Science fromGovernor Perdue in 2012, the highest honor given to a civilian by the state. Hewas declared among the Top 35 Thinkers India has produced since 1975 by IndiaToday magazine in 2012. The Russian Federation honored him in 2015 with theGlobal Energy Prize to recognize the impact of his IGBT innovation on energydistribution, energy generation, and energy conservation. He was inducted into theNational Inventors Hall of Fame in 2016 as the sole inventor of the IGBT. Hisprolific academic inventorship was recognized in 2017 by induction into theNational Academy of Inventors.

xxxii About the Author