Modeling of Wide Bandgap Power Semiconductor Devices—Part I Kang Peng, University of South Carolina

University of South Carolina From the SelectedWorks of Kang Peng Winter November 26, 2016 Modeling of Wide Bandgap Power Semiconductor Devices—Part I Kang Peng, University of South Carolina Available at: https://works.bepress.com/kang-peng/2/ IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 62, NO. 2, FEBRUARY 2015 423 Modeling of Wide Bandgap Power Semiconductor Devices—Part I Homer Alan Mantooth, Fellow, IEEE, Kang Peng, Student Member, IEEE, Enrico Santi, Senior Member, IEEE, and Jerry L. Hudgins, Fellow, IEEE (Invited Paper) Abstract— Wide bandgap power devices have emerged as an frequency of operation. This has created a growing need for often superior alternative power switch technology for many power device technologies that can deliver high temperature, power electronic applications. These devices theoretically have high-power density, and high-frequency operation. For excellent material properties enabling power device operation at higher switching frequencies and higher temperatures compared example, a variety of applications in the aircraft, automotive, with conventional silicon devices. However, material defects and energy exploration industries require power conversion can dominate device behavior, particularly over time, and this systems to operate at an ambient temperature significantly should be strongly considered when trying to model actual > 200 °C, far beyond Si material limits. Consequently, a new characteristics of currently available devices. Compact models generation of so-called wide bandgap semiconductor devices of wide bandgap power devices are necessary to analyze and evaluate their impact on circuit and system performance. has emerged as viable replacements for the current Si-based Available compact models, i.e., models compatible with circuit- power devices. level simulators, are reviewed. In particular, this paper presents A substantial amount of research and development activity a review of compact models for silicon carbide power diodes and has occurred over the past 20 years in the silicon carbide (SiC) MOSFETs. and gallium nitride (GaN) fields. These efforts have deliv- Index Terms— Gallium-nitride (GaN), modeling, power device ered several classes of power semiconductor devices, with modeling, power semiconductor devices, silicon-carbide (SiC), voltage ratings from 30 V to 15 kV and growing, for a wide wide bandgap. variety of applications. Circuit and system researchers have collaborated in parallel to demonstrate the efficacy of these I. INTRODUCTION device technologies in demonstration designs ranging from OWER electronics can be defined as the application of laptop chargers (200 V) to plug-in hybrid electric vehicle Psolid-state electronics to condition, control, and convert battery chargers (1200 V) to fault current limiters for the electric power. With increasing concern for energy delivery electric power grid (10 kV). The ability of these devices to and environmental protection, power electronics is playing an switch at higher frequencies than their Si counterparts has increasingly important role in human society. Power semi- led to system-level benefits in volume or efficiency even at conductor devices are the core solid-state components in operational temperatures where Si is suitable. the overall power conversion system, and they most often At present, SiC and GaN are the most promising among consume the largest portion of power losses in that system. all wide bandgap semiconductor materials [1]. Table I [2] Therefore, the development of power semiconductor devices compares the material properties of Si, SiC, and GaN. The SiC has been the driving force in the progress of power elec- and GaN have almost a three times larger bandgap (∼3eV) tronics systems. Recently, silicon (Si)-based devices have compared with Si (∼1 eV). The breakdown electric field of dominated the power device market due to mature and well- SiC and GaN is one order of magnitude higher than that established fabrication technology for Si. However, there of Si. The higher breakdown electric field enables the design have been applications where Si power electronics have not of wide bandgap power devices with thinner and higher doped made the inroads necessary for widespread deployment due voltage-blocking layers. For unipolar power devices, this can to insufficient thermal capabilities, voltage breakdown, or yield a lower ON-state voltage drop and conduction loss. For bipolar power devices, this can lead to a shorter switching Manuscript received August 12, 2014; revised October 20, 2014; accepted October 23, 2014. Date of publication November 26, 2014; date of current time and lower switching loss. The high thermal conductivity version January 20, 2015. This work was supported by the Office of Naval of SiC, together with the large bandgap, allows SiC-based Research, Arlington, VA, USA, under Grant N00014-08-1-0080. The review devices to operate at temperatures easily exceeding 200 °C. of this paper was arranged by Editor N. Ohtani. H. A. Mantooth is with the University of Arkansas, Fayetteville, AR 72701 All of these properties make wide bandgap semiconductor USA (e-mail: [email protected]). devices a promising alternative to Si-based devices. K. Peng and E. Santi are with the Department of Electrical Engineer- Substantial improvements in GaN and SiC material quality ing, University of South Carolina, Columbia, SC 29208 USA (e-mail: [email protected]; [email protected]). over the past several years have led to the availability of J. L. Hudgins is with the Department of Electrical Engineering, University commercial SiC and GaN power devices. In particular, SiC of Nebraska—Lincoln, Lincoln, NE 68588 USA (e-mail: [email protected]). Schottky diodes, MOSFETs, and junction gate FETs (JFETs) Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. have reached the market. Although GaN-based devices can Digital Object Identifier 10.1109/TED.2014.2368274 theoretically offer better performance than SiC, the lack 0018-9383 © 2014 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications_standards/publications/rights/index.html for more information. 424 IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 62, NO. 2, FEBRUARY 2015 TABLE I turn-OFF thyristors, and IGBTs, were modeled in addi- MATERIAL PROPERTIES tion to bipolar junction transistors (BJTs) and SiC junction transistors [6]. This paper presents a survey of recent progress on SiC- and GaN-based power semiconductor devices along with their device models. In Section II, an overview of device modeling requirements is given, and five different device model levels are described. An SiC power devices are described in Section III, while GaN power devices are presented in Section IV. Throughout this paper, a description of reliability issues associated with these wide bandgap devices is provided. Some assertions regarding outstanding issues and future trends of power device modeling are provided in the of good-quality substrates hinders the development of high concluding section. voltage vertical GaN power devices. However, the interest in GaN power devices by industry is increasing. II. COMPACT DEVICE MODEL REQUIREMENTS Nevertheless, material defects are a root cause of device failures. These defects and corresponding secondary effects The basic objective in compact device modeling is to are exacerbated by additional energy from high electric fields, achieve a predictive description of the current flow through large current densities, increasing temperature, and interface the device as a function of the applied voltages and currents, stress of material layers. For example, nonmicropipe defects in environmental conditions, such as temperature and radiation, the bulk and epitaxial layers of SiC have been reported to limit and physical characteristics, such as geometry, doping levels, the current and voltage ratings in devices and have contributed and so on. Understanding this objective and the mathematical to degraded performance and failure [3]. The bottom line formulation that is consistent with the numerical algorithms question is whether SiC and GaN can meet or exceed Si used by circuit simulators to analyze circuits and systems, Failure In Time (FIT) (10−9 failures per device operation hour) is the first step in understanding how to create compact levels to take advantage of a projected significant increase models that are predictive of device behavior and also run at in power density in wide bandgap devices. This improved computationally attractive speeds. For device models, at least power density typically means higher operating temperatures, a good approximation to the actual relationship of the elec- greater thermal cycling, higher impressed electric fields - trical variables needs to be obtained. A compromise between all in opposition to device reliability. Yet presently, some computational speed and model accuracy is usually made. The second-generation SiC Schottky diodes are reported to have required accuracy and simulation time are crucial factors con- a failure rate of < 0.15 ppm. In addition, some SiC junction- sidered by device model designers when making this tradeoff. barrier Schottky (JBS) diodes have achieved a failure rate A very simple device model generally provides fast simulation of <0.5 failures per billion of operational hours (0.5 FIT) [4]. speed but loses physics insight into power device behavior and Meanwhile, looking at comparison with silicon

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