Silicon carbide PiN and merged PiN Schottky power diode models implemented in the Saber circuit simulator

Dynamic electrothermal circuit simulator models are developed for silicon carbide power diodes. The models accurately describe the temperature dependence of on-state characteristics and reverse-recovery switching waveforms. The models are verified for the temperature dependence of the on-state characteristics, and the di/dt, dv/dt, and temperature dependence of the reverse-recovery characteristics. The model results are presented for 1500 V SiC Merged PiN Schottky (MPS) diodes, 600 V Schottky diodes, and 5000 V SiC PiN diodes. The devices studied have current ratings from 0.25 A to 5 A and have different lifetimes resulting in different switching energy versus on-state voltage trade-offs. The devices are characterized using a previously reported test system specifically designed to emulate a wide range of application conditions by independently controlling the applied diode voltage, forward diode current, di/dt, and dv/dt at turn-off. A behavioral model of the test system is implemented to simulate and validate the models. The models are validated for a wide range of application conditions for which the diode could be used.     

一种带P型埋层的4H-SiC PiN二极管

碳化硅(SiC)PiN二极管是应用在高压大功率整流领域中的一种重要的功率二极管。受SiC外延材料的载流子寿命限制以及常规SiC PiN二极管较低的阳极注入效率的影响,SiC PiN二极管的正向导通性能较差,这极大限制了其在高压大电流领域的应用。文章提出了一种带P型埋层的4H-SiC PiN二极管,较常规SiC PiN二极管增强了阳极区的少子注入效率,降低了器件的导通电阻,增大了正向电流。仿真结果表明,当正向偏压为5 V时,引入P型埋层的SiC PiN二极管的正向电流密度比常规SiC PiN二极管提升了52.8%。     

Performance evaluation of a Schottky SiC power diode in a boost PFC application

The performance of a 600 V, 4 A silicon carbide (SiC) Schottky diode (Infineon SDP04S60) is experimentally evaluated. A 300 W boost power factor corrector (PFC) with average current mode control is considered as a key application. Measurements of overall efficiency, switch and diode losses, and conducted electromagnetic interference (EMI) are performed both with the SiC diode and with two ultra-fast, soft-recovery, silicon power diodes, namely the RURD460 and the presented STTH5R06D. The paper compares the results to quantify the impact of the recovery current reduction provided by SiC diode on these key aspects of the converter behavior. Based on the experimental results, the paper shows that the use of SiC diodes in PFC designs may only be justified in high switching frequency applications.     

碳化硅MPS:新一代功率开关二极管

碳化硅MPS(Merged PiN Schottky diode)具有很好的开关特性，并具有PiN二极管高阻断电压、低漏电流和SBD小开启电压，大导通电流以及高开关速度的优点，是最有希望的新一代功率开关二极管。文章系统地介绍了碳化硅MPS的结构和性能。理论和实验分析表明，碳化硅材料的优异性能与MPS结构的优势相结合，是当今功率开关管发展的趋势。     

碳化硅器件发展概述

概要介绍了第三代半导体材料碳化硅(SiC)在高温、高频、大功率器件应用方面的优势,结合国际上SiC肖特基势垒二极管,PiN二极管和结势垒肖特基二极管的发展历史,介绍了SiC功率二极管的最新进展,同时对我国宽禁带半导体SiC器件的研究现状及发展方向做了概述及展望。     

Characterization of hard- and soft-switching performance of high-voltage Si and 4H-SiC PiN diodes

This paper presents a study of the performance of high-voltage Si and 4H-SiC diodes in a DC-DC buck converter. Device operation in both hard- and zero-voltage switching conditions is presented with the help of measurements and two-dimensional (2-D) mixed device-circuit simulations. Experimental results show that SiC PiN diodes have a strong potential for use in high-speed high-voltage power electronics applications operating at high temperature. A combination of low excess carrier concentration and low carrier lifetime results in superior switching performance of the 4H-SiC diode over ultrafast Si diodes. Soft switching is shown to minimize the switching loss and allow operation at higher switching frequencies using Si diodes. The power loss of 4H-SiC diodes is dominated by conduction loss. Consequently, soft-switching techniques result in a marginal reduction in power loss. However, the low overall power loss implies that SiC diodes can be used at very high switching frequencies even in hard-switching configurations.     

SiC power Schottky and PiN diodes

The present state of SiC power Schottky and PiN diodes are presented in this paper. The design, fabrication, and characterization of a 130 A Schottky diode, 4.9 kV Schottky diode, and an 8.6 kV 4H-SiC PiN diode, which are considered to be significant milestones in the development of high power SiC diodes, are described in detail. Design guidelines and practical issues for the realization of high-power SiC Schottky and PiN diodes are also presented. Experimental results on edge termination techniques applied to newly developed, extremely thick (e.g., 85 and 100 μm) 4H-SiC epitaxial layers show promising results. Switching and high-temperature measurements prove that SiC power diodes offer extremely low loss alternatives to conventional technologies and show the promise of demonstrating efficient power circuits. At sufficiently high on-state current densities, the on-state voltage drop of Schottky and PiN diodes have been shown to be comparable to those offered by conventional technologies     

混合PiN/Schottky二极管的研究

对混合PiN/Schottky二极管（MPS）进行研究,首先对MPS二极管的工作原理进行了分析,通过对MPS二极管、肖特基二极管、PIN二极管的伏安特性进行模拟,结果表明MPS二极管正向压降小,电流密度大,反向漏电流小,是一种具有肖特基正向特性和PN结反向特性的新型整流器。可以通过改变肖特基和PN结的面积比来调整MPS二极管的性能,与肖特基二极管和PIN二极管相比具有明显的优势,是功率系统不可或缺的功率整流管。     

Characterization of SiC Schottky diodes at different temperatures

The emergence of silicon carbide (SiC) based power semiconductor switches, with their superior features compared with silicon (Si) based switches, has resulted in substantial improvement in the performance of power electronics converter systems. These systems with SiC power devices have the qualities of being more compact, lighter, and more efficient; thus, they are ideal for high-voltage power electronics applications. In this study, commercial Si pn and SiC Schottky diodes are tested and characterized, their behavioral static and loss models are derived at different temperatures, and they are compared with respect to each other.     

用于高功率密度功率因素校正的新一代600V砷化镓肖特基二极管

在200W连续导通模式功率因数校正（PFC）系统中，新一代600V砷化镓（GaAs）肖特基二极管与硅和碳化硅（SiC）二级管比较，砷化镓、碳化硅在PFC系统中的损耗减少高达25％。由于砷化镓有较低的结电容，砷化镓相对碳化硅高的通态损耗被较低的MOSFET损耗弥补了。和碳化硅技术相比，砷化镓有成本和可靠性优势。对于高频和高密度应用来说，新一代的砷化镓二级管是很有前景的。     

High-voltage 4H-SiC PiN diodes with the etched implant junction termination extension

This paper presents the design and fabrication of an etched implant junction termination extension(JTE) for high-voltage 4H-SiC PiN diodes. Unlike the conventional JTE structure, the proposed structure utilizes multiple etching steps to achieve the optimum JTE concentration range. The simulation results show that the etched implant JTE method can improve the blocking voltage of SiC PiN diodes and also provides broad process latitude for parameter variations, such as implantation dose and activation annealing condition. The fabricated SiC PiN diodes with the etched implant JTE exhibit a highest blocking voltage of 4.5 kV and the forward on-state voltage of 4.6 V at room temperature. These results are of interest for understanding the etched implant method in the fabrication of high-voltage power devices.     

Compact models for silicon carbide power devices

Compact silicon carbide (SiC) power semiconductor device models for circuit simulation have been developed for power Schottky, merged-PiN-Schottky, PiN diodes, and MOSFETs. In these models, the static and dynamic performance of the power SiC devices requires specific attention to the low-doped, voltage blocking drift region; the channel transconductance in MOS devices; the relatively low-intrinsic carrier concentration; the incomplete ionization of dopants; and the temperature dependent material properties. The modeling techniques required to account for each of these characteristics are described.     

SiC devices: physics and numerical simulation

The important material parameters for 6H silicon carbide (6H-SiC) are extracted from the literature and implemented into the 2-D device simulation programs PISCES and BREAKDOWN and into the 1-D program OSSI Simulations of 6H-SiC p-n junctions show the possibility to operate corresponding devices at temperatures up to 1000 K thanks to their low reverse current densities. Comparison of a 6H-SiC 1200 V p-n^--n⁺ diode with a corresponding silicon (Si) diode shows the higher switching performance of the 6H-SiC diode, while the forward power loss is somewhat higher than in Si due to the higher built-in voltage of the 6H-SiC p-n junction. This disadvantage can be avoided by a 6H-SiC Schottky diode. The on-resistances of Si, 3C-SiC, and 6H-SiC vertical power MOSFET's are compared by analytical calculations. At room temperature, such SiC MOSFET's can operate up to blocking capabilities of 5000 V with an on-resistance below 0.1 Ωcm², while Si MOSFET's are limited to below 500 V. This is checked by calculating the characteristics of a 6H-SiC 1200 V MOSFET with PISCES. In the voltage region below 200 V, Si is superior due to its higher mobility and lower threshold voltage. Electric fields in the order of 4×10⁶ V/cm occur in the gate oxide of the mentioned 6H-SiC MOSFET as well as in a field plate oxide used to passivate its planar junction. To investigate the high frequency performance of SiC devices, a heterobipolartransistor with a 6H-SiC emitter is considered. Base and collector are assumed to be out of 3C-SiC. Frequencies up to 10 GHz with a very high output power are obtained on the basis of analytical considerations     

Characterization, Modeling, and Application of 10-kV SiC MOSFET

Ten-kilovolt SiC MOSFETs are currently under development by a number of organizations in the United States, with the aim of enabling their applications in high-voltage high-frequency power conversions. The aim of this paper is to obtain the key device characteristics of SiC MOSFETs so that their realistic application prospect can be provided. In particular, the emphasis is on obtaining their losses in various operation conditions from the extensive characterization study and a proposed behavioral SPICE model. Using the validated MOSFET SPICE model, a 20-kHz 370-W dc/dc boost converter based on a 10-kV 4H-SiC DMOSFET and diodes is designed and experimentally demonstrated. In the steady state of the boost converter, the total power loss in the 15.45- $hbox{mm}^{2}$ SiC MOSFET is 23.6 W for the input power of 428 W. The characterization study of the experimental SiC MOSFET and the experiment of the SiC MOSFET-based boost converter indicate that the turn-on losses of SiC MOSFETs are the dominant factors in determining their maximum operation frequency in hard-switched circuits with conventional thermal management. Replacing a 10-kV SiC PiN diode with a 10-kV SiC JBS diode as a boost diode and using a small external gate resistor, the turn-on loss of the SiC MOSFET can be reduced, and the 10-kV 5-A SiC MOSFET-based boost converter is predicted to be capable of a 20-kHz operation with a 5-kV dc output voltage and a 1.25-kW output power by the PSpice simulation with the MOSFET model. The low losses and fast switching speed of 10-kV SiC MOSFETs shown in the characterization study and the preliminary demonstration of the boost converter make them attractive in high-frequency high-voltage power-conversion applications.      

Static and dynamic characterization of large-areahigh-current-density SiC Schottky diodes

The static and dynamic characteristics of large-area, high-voltage 4H-SiC Schottky barrier diodes are presented. With a breakdown voltage greater than 1200 V and a forward current in excess of 6 A at 2 V forward bias, these devices enable for the first time the evaluation of SiC Schottky diodes in practical switching circuits. These diodes were inserted into standard test circuits and compared to commercially available silicon devices, the results of which are reported here. Substituting SiC Schottky diodes in place of comparably rated silicon PIN diodes reduced the switching losses by a factor of four, and virtually eliminated the reverse recovery transient. These results are even more dramatic at elevated temperatures. While the switching loss in silicon diodes increases dramatically with temperature, the SiC devices remain essentially unchanged. The data presented here clearly demonstrates the distinct advantages offered by SiC Schottky rectifiers, and their emerging potential to replace silicon PIN diodes in power switching applications     

Schottky diode design for low-voltage rectification

Barrier height and impurity concentration of a power Schottky diode are optimized for maximum rectifying efficiency in DC-DC converter operation. An optimum barrier-height-impurity-concentration combination is calculated for a given output voltage and diode temperature. For a 1.5 – 2 V output converter, the optimum combination is found to be 17 kT/q and 1.5 × 10¹⁶ cm^?3. Based on the theoretical prediction, titanium- and hafnium-barrier diodes were fabricated as suitable diodes for low-voltage converters and compared with conventionally used molybdenum-barrier diodes. In the experiment on a 2-V output DC-DC converter, the new diodes show higher efficiency than molybdenum diodes at up to 85°C. They are fit for use in encapsulated converters because of their smaller heat generation.     

Theoretical comparison of SiC PiN and Schottky diodes based on power dissipation considerations

In order to select the optimal device for a particular application, designers must carefully analyze the tradeoffs between competing devices. Recent progress in SiC power rectifiers has resulted in the demonstration of high-voltage PiN and Schottky barrier diodes (SBDs). With both technologies maturing, power electronics engineers will soon face the task of selecting between these two devices. Until recently, the choice was simple, since silicon SBDs are only available for relatively low voltage applications. The choice is not as clear when considering SiC diodes, and guidelines for determining the proper application of each are needed. The purpose of this paper is to provide such guidelines, based on an analysis of the most significant tradeoffs involved.     

SiC/Si heterojunction diodes fabricated by self-selective and byblanket rapid thermal chemical vapor deposition

SiC/Si heterojunction diodes have been fabricated by two different rapid thermal chemical vapor deposition (RTCVD) processes: a localized self-selective growth and blanket growth. The self-selective growth of crystalline cubic (β) SiC was obtained by propane carbonization of the Si substrate in regions unprotected by an SiO₂ layer, producing planar diodes. Mesa diodes were fabricated using the blanket growth of polycrystalline β-SiC produced by the decomposition of methylsilane (CH₃SiH₃). The SiC/Si heterojunction diodes show good rectifying properties for both device structures. Reverse breakdown voltage of 50 V was obtained with the self-selective SiC/Si diode. The mesa diodes exhibited even higher breakdown voltages (V_br) of 150 V and excellent ideality factors of 1.06 at 25°C. The high V_br and good forward rectifying characteristics indicate that the SiC/Si heterojunction diode represents a promising approach for the fabrication of wide-gap emitter SiC/Si heterojunction bipolar transistors     

A 1-MHz hard-switched silicon carbide DC-DC converter

Silicon Carbide (SiC) is a wide bandgap semiconductor material that offers performance improvements over Si for power semiconductors with accompanying benefits for power electronics applications that use these semiconductors. The wide bandgap of SiC results in higher junction forward voltage drops, so SiC is best suited for majority carrier devices such as field effect transistors (FETs) and Schottky diodes. The wide bandgap of SiC results in it having a high breakdown electric field, which in turn results in lower resistivity and narrower drift regions in power devices. This dramatically lowers the resistance of the drift region and means that SiC devices with substantially less area than their corresponding Si devices can be used. The lower device area reduces the capacitance of the devices enabling higher frequency operation. Here, the results from a 1-MHz hard-switched dc-dc converter employing SiC JFETs and Schottky diodes will be presented. This converter was designed to convert 270Vdc to 42Vdc such as may be needed in future electric cars. The results provide the performance obtained at 1MHz and demonstrate the feasibility of a hard-switched dc-dc converter operating at this frequency.     

An accurate electro-thermal model for merged SiC PiN Schottky diodes

The paper presents a SiC merged PiN Schottky diode model dedicated to the dynamic as-well-as very accurate static simulation. The model takes into account the temperature dependence of device characteristics and combines in a single model the behaviour typical for bipolar and unipolar devices. The presented electro-thermal simulations of the diode produce accurate results, consistent with the measurements. The dynamic model verification has been also presented on the example of a boost power converter.