Evaluation of high-voltage 4H-SiC switching devices

In this paper, the on-state and switching performance of 4H-SiC UMOSFETs, TIGBTs, BJTs, SIThs, and GTOs with voltage ratings from 1 to 10 kV are simulated at different temperatures. Comparison with silicon devices highlights the advantages of SiC technology. SiC BJTs suffer the same problem as Si BJTs, namely the degradation of current gain with increased voltage rating which makes them unsuitable for applications above 4 kV. SiC MOSFETs dominate applications below 4 kV for their attractive conduction performance and advantages such as ease of use. Above 3 kV, SiC MOSFETs are not as attractive as SiC bipolar devices because of their high on-state voltages. In the voltage range simulated, SiC IGBTs, SIThs, and GTOs have comparable current handling ability. Considering the GTOs slow switching speed and drive complexities, IGBTs and SIThs are a better choice in the voltage range 4-10 kV. Calculations based on conduction loss and switching loss indicate that SiC SIThs are superior to IGBTs except in high-temperature and high-frequency applications where IGBTs are better. The need to provide a large gate current during turnoff and turn-off failure caused by gate debiasing, decreases the attractiveness of the SITh     

4H-SiC双层浮结肖特基势垒二极管温度特性研究

为了增强器件高温条件下的适应性,对4H-SiC双层浮结肖特基势垒功率二极管的温度特性进行了研究.结果表明,当温度变化时,器件的阻断电压、通态电阻、反向漏电流及开关时间等电学性质均要发生一定的变化.作为一种基于浮结技术的sic新器件,通过数值模拟方法对其特征参数进行优化,可使其承载电流能力、阻断特性和开关速度等得到进一步...     

Silicon Carbide Power MOSFET Model and Parameter Extraction Sequence

A compact circuit simulator model is used to describe the performance of a 2-kV, 5-A 4-H silicon carbide (SiC) power DiMOSFET and to perform a detailed comparison with the performance of a widely used 400-V, 5-A Si power MOSFET. The model's channel current expressions are unique in that they include the channel regions at the corners of the square or hexagonal cells that turn on at lower gate voltages and the enhanced linear region transconductance due to diffusion in the nonuniformly doped channel. It is shown that the model accurately describes the static and dynamic performance of both the Si and SiC devices and that the diffusion-enhanced channel conductance is essential to describe the SiC DiMOSFET on-state characteristics. The detailed device comparisons reveal that both the on-state performance and switching performance at 25degC are similar between the 400-V Si and 2-kV SiC MOSFETs, with the exception that the SiC device requires twice the gate drive voltage. The main difference between the devices is that the SiC has a five times higher voltage rating without an increase in the specific on-resistance. At higher temperatures (above 100degC), the Si device has a severe reduction in conduction capability, whereas the SiC on-resistance is only minimally affected     

SiC肖特基栅JFET功率特性的研究

提出了一种新型结构的SiC结型场效应晶体管,采用肖特基接触替代P+型栅区,以降低SiC JFET的工艺复杂度,并提高器件的功率特性。建立了器件的数值模型,对不同材料和结构参数下的功率特性进行了仿真。结果表明,与PN结栅相比,肖特基栅结构可以有效降低SiC JFET的开态电阻;与常规结构的双极模式SiC JFET相比,在SiC肖特基栅JFET的栅极正偏注入载流子,同样可以有效降低器件的开态电阻,折中器件的正反向特性,但不会延长开关时间。     

Power ICs in the saddle

Improving the voltage, current, and switching capabilities of power electronics devices makes for more efficient control of power and energy. Interface with microprocessors for protection from unfriendly environments is also an asset. The author discusses the development of power electronic devices using MOSFETs, insulated gate transistors, and MOS controlled thyristors. The future of SiC based devices is also discussed     

High-Voltage Auxiliary Power Supply Using Series-Connected MOSFETs and Floating Self-Driving Technique

This paper deals with high-voltage auxiliary switching-mode power supplies (SMPSs). An overview of the state of the art is given, and a novel solution is proposed. The proposed solution is based on a single-ended flyback or forward topology with the main switch arranged as a series connection of two metal-oxide-semiconductor field-effect transistors (MOSFETs). The bottom MOSFET is driven directly by an ordinary control circuit and gate driver, while the top MOSFET is driven by a floating self-supplied gate driver. The floating gate driver is connected to the input filter capacitors' midpoint. This gate driver plays two roles: driving of the top MOSFET and control of distribution of the blocking voltage among the series-connected MOSFETs, in steady state as well as during commutation. The series connection of lower voltage MOSFETs has two important advantages compared to that of a single high-voltage MOSFET: lower conduction losses and lower cost. When several switches are series connected, each switch supports a fraction of the total blocking voltage, and therefore, each switch can be rated for lower voltage. The total on-state resistance and the cost of such a switch arrangement are lower compared to that of a single switch that supports the full blocking voltage. The proposed SMPS is theoretically analyzed and experimentally verified. The experimental results are presented and discussed.     

Resonant gate driver with efficient gate energy recovery and switching loss reduction

This article describes a novel resonant gate driver for charging the gate capacitor of power metal-oxide semiconductor field-effect-transistors (MOSFETs) that operate at a high switching frequency in power converters. The proposed resonant gate driver is designed with three small MOSFETs to build up the inductor current in addition to an inductor for temporary energy storage. The proposed resonant gate driver recovers the CV² gate loss, which is the largest loss dissipated in the gate resistance in conventional gate drivers. In addition, the switching loss is reduced at the instants of turn on and turn off in the power MOSFETs of power converters by using the proposed gate driver. Mathematical analyses of the total loss appearing in the gate driver circuit and the switching loss reduction in the power switch of power converters are discussed. Finally, the proposed resonant gate driver is verified with experimental results at a switching frequency of 1 MHz.     

High breakdown Voltage undoped AlGaN-GaN power HEMT on sapphire substrate and its demonstration for DC-DC converter application

Undoped AlGaN-GaN power high electron mobility transistors (HEMTs) on sapphire substrate with 470-V breakdown voltage were fabricated and demonstrated as a main switching device for a high-voltage dc-dc converter. The fabricated power HEMT realized a high breakdown voltage with a field plate structure and a low on-state resistance of 3.9 m/spl Omega//spl middot/cm/sup 2/, which is 10 /spl times/ lower than that of conventional Si MOSFETs. The dc-dc converter operation of a down chopper circuit was demonstrated using the fabricated device at the input voltage of 300 V. These results show the promising possibilities of the AlGaN-GaN power HEMTs on sapphire substrate for future switching power devices.     

Planar Power MOSFETs for Smart Power CMOS Switches

Planar power MOSFETs with an octagonal gate are designed, fabricated, and tested. The implantation dose of the pinch-resistor region is optimized for off-state breakdown voltage times on-state resistance by computer simulation.     

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.     

SiC电力电子器件研究现状及新进展

由于硅材料本身的限制,传统硅电力电子器件性能已经接近其极限,碳化硅(SiC)器件的高功率、高效率、耐高温、抗辐照等优势逐渐突显,成为电力电子器件一个新的发展方向.综述了SiC材料、SiC电力电子器件、SiC模块及关键工艺的研究现状,重点从材料、器件结构、制备工艺等方面阐述了SiC二极管、金属氧化物半导体场效应晶体管(MOSFET)、结晶型场效应晶体管(JFET)、双极结型晶体管(BJT)、绝缘栅双极晶体管(IGBT)及模块的研究进展.概述了SiC材料、SiC电力电子器件及模块的商品化情况,最后对SiC材料及器件的发展趋势进行了展望.     

High-power-density 4H-SiC RF MOSFETs

The authors have made the first 4H-SiC RF power MOSFETs with cutoff frequency up to 12 GHz, delivering RF power of 1.9 W/mm at 3 GHz. The transistors withstand 200 V drain voltage, are normally off, and show no gate lag, which is often encountered in SiC MESFETs. The measured devices have a single drain finger and a double gate finger, and a total gate width of 0.8 mm. To their knowledge, this is the first time that power densities above 1 W/mm at 3 GHz are reported for SiC MOSFETs.     

SiC电力电子器件对电力系统的影响

宽禁带SiC材料被认为是高性能电力电子器件的理想材料,比较了Si和SiC材料的电力电子器件在击穿电场强度、稳定性和开关速度等方面的区别,着重分析了以SiC器件为功率开关的电力电子装置对电力系统中柔性交流输电系统(FACTS)、高压直流输电(HVDC)装置、新能源技术和微电网技术领域的影响。分析表明,SiC电力电子器件具有耐高压、耐高温、开关频率高、损耗小、动态性能优良等特点,在较高电压等级(高于3 kV)或对电力电子装置性能有更高要求的场合,具有良好的应用前景。     

Power M.O.S. devices

In this paper, the major structures and electric properties of the relatively new power MOSFETs are presented. The basic concepts are dealt with first, with a view to increasing the current and voltage capabilities in M.O.S. transistors; and then the way in which they are applied to the so far most promising power structures i.e. V.MOS and VD.MOS transistors, is shown.The electric properties of these devices are then described i.e. threshold voltage, voltage current characteristics: ohmic, saturation and quasi-saturation ranges, first and second breakdown, safe operating area. Some dynamic behavior aspects are also considered. To conclude, one of the fundamental limitations of power MOSFETs is analyzed i.e. the on-state resistance vs. voltage handling capability trade-off and some data for comparison with other power devices is also provided.     

IEGT的高温特性与闩锁失效分析(英文)

介绍了平面栅电子注入增强型栅极晶体管(IEGT)的闩锁效应,讨论了温度对关键特性参数如通态压降、正向阻断电压及开关时间的影响。利用ISE软件模拟了IEGT在高温下的导通特性、阻断特性和开关特性,分析了IEGT在高温下的失效原因,提出了改善其高温安全工作区(SOA)的措施。     

一种200V/100A VDMOS器件开发

分析了功率MOSFET最大额定电流与导通电阻的关系,讨论了平面型中压大电流VDMOS器件设计中导通电阻、面积和开关损耗的折衷考虑,提出了圆弧形沟道布局以增大沟道宽度,以及栅氧下部分非沟道区域采用局域氧化技术以减小栅电容的方法,并据此设计了一种元胞结构。详细论述了器件制造过程中的关键工艺环节,包括栅氧化、光刻套准、多晶硅刻蚀、P阱推进等。流水所得VDMOS实测结果表明,该器件反向击穿特性良好,栅氧耐压达到本征击穿,阈值电压2.8V,导通电阻仅25mΩ,器件综合性能良好。     

碳化硅MOSFET反型沟道迁移率的研究

SiC MOSFET是制作高速、低功耗开关功率器件的理想材料，然而，制作反型沟道迁移率较高的SiC MOSFET工艺尚未取得满意结果。通过在N0中高温退火可以显著地提高4H—SiC MOSFET的有效沟道迁移率；采用H2中退火制作的4H—SiC MOSFET阈值电压为3．1V，反型沟道迁移率高于100cm^2／Vs的栅压的安全工作区较宽。N20退火技术由于其的安全性而发展迅速并将取代N0。     

SiC JBS二极管和SiC MOSFET的空间辐照效应及机理

基于第六代650 V 碳化硅结型肖特基二极管(SiC JBS Diode)和第三代900 V 碳化硅场效应晶体管(SiC MOSFET),开展SiC功率器件的单粒子效应、总剂量效应和位移损伤效应研究。20~80 MeV质子单粒子效应实验中,SiC功率器件发生单粒子烧毁(SEB)时伴随着波浪形脉冲电流的产生,辐照后SEB器件的击穿特性完全丧失。SiC功率器件发生SEB时的累积质子注量随偏置电压的增大而减小。利用计算机辅助设计工具(TCAD)开展SiC MOSFET的单粒子效应仿真,结果表明,重离子从源极入射器件时,具有更短的SEB发生时间和更低的SEB阈值电压。栅-源拐角和衬底-外延层交界处为SiC MOSFET的SEB敏感区域,强电场强度和高电流密度的同时存在导致敏感区域产生过高的晶格温度。SiC MOSFET在栅压偏置(U_GS=3 V,U_DS=0 V)下开展钴源总剂量效应实验,相比于漏压偏置(U_GS=0 V,U_DS=300 V)和零压偏置(U_GS=U_DS=0 V),出现更严重的电学性能退化。利用中带电压法分析发现,栅极偏置下氧化层内的垂直电场提升了陷阱电荷的生成率,加剧了阈值电压的退化。中子位移损伤会导致SiC JBS二极管的正向电流和反向电流减小。在漏极偏置下进行中子位移损伤效应实验,SiC MOSFET的电学性能退化最严重。该研究为空间用SiC器件的辐射效应机理及抗辐射加固研究提供了一定的参考和支撑。     

Off-state degradation with ac bias in PMOSFET

For the first time, the current failure of p-channel MOSFETs used for the sub-wordline driver of state-of-the-art DRAM chips was investigated during off-state switching cycles. With increasing switching speed for the sub-wordline driver, the subthreshold leakage current of p-channel MOSFETs increased, and resulted in serious stand-by current failure. The model proposed in this work suggested that the off-state degradation of p-channel MOSFETs with ac bias will intensify as the dimensions of devices decrease due to both the high electric field and the high operating frequency. The roles of various device parameters- such as gate length, gate-tab width, doping concentration at the source/drain extensions, operating temperature and operating frequency- on the degradation of p-channel MOSFETs were investigated.     

The future of power semiconductor device technology

Power electronic systems have benefited greatly during the past ten years from the revolutionary advances that have occurred in power discrete devices. The introduction of power metal-oxide-semiconductor field-effect transistors (MOSFETs) in the 1970s and the insulated gate bipolar transistors (IGBTs) in the 1980s enabled design of very compact high-efficiency systems due to the greatly enhanced power gain resulting from the high input impedance of these structures. Recently, significant improvements in the performance of silicon-power MOSFETs has been achieved by using innovative vertical structures with charge coupled regions. Meanwhile, silicon IGBTs continue to dominate the medium- and high-voltage application space sue to scaling of their voltage ratings and refinements to their gate structure achieved by using very large scale integration (VLSI) technology and trench gate regions. Research on a variety of MOS-gated thyristors has also been conducted, resulting in some promising improvements in the tradeoff between on-state power loss, switching power loss, and the safe-operating-area. Concurrent improvements in power rectifiers have been achieved at low-voltage ratings using Schottky rectifier structures containing trenches and at high-voltage ratings using structures that combine junction and Schottky barrier contacts. On the longer term, silicon carbide Schottky rectifiers and power MOSFETs offer at least another tenfold improvement in performance. Although the projected performance enhancements have been experimentally demonstrated, the defect density and cost of the starting material are determining the pace of commercialization of this technology at present