GaN基电力电子器件关键技术的进展

氮化镓GaN(gallium nitride)材料非常适合应用于高频、高功率、高压的电子电力器件当中。目前,GaN功率电子器件技术方案主要分为Si衬底上横向结构器件和Ga N自支撑衬底上垂直结构器件2种。其中,横向结构器件由于制造成本低且有良好的互补金属-氧化物-半导体CMOS(complementary metal-oxide-semiconductor)工艺兼容性已逐步实现产业化,但是存在材料缺陷多、常关型难实现、高耐压困难以及电流崩塌效应等问题;垂直结构器件能够在不增大芯片尺寸的条件下实现高击穿电压,具有非常广阔的市场前景,也面临着材料生长、器件结构设计和可靠性等方面的挑战。基于此,主要针对这两种器件综述介绍并进行了展望。     

垂直结构氮化镓功率晶体管的材料与工艺问题

硅功率器件已接近其理论物理性能的极限。基于宽禁带半导体材料的电力电子系统能够实现更高的功率密度和电能转换效率,而具有高临界电场和载流子迁移率的氮化镓被认为是未来高功率、高频和高温应用的最有希望的候选者之一,而由品质因子给出的氮化镓基功率器件的综合性能具有大于1 000倍于硅器件的理论极限。目前已产业化的氮化镓功率晶体管主要基于水平结构,但垂直结构更有利于实现更高电压和更大电流。随着氮化镓衬底材料的逐渐成熟,近期垂直结构氮化镓功率器件成为了学术界和产业界的研究热点,并被认为是下一代650～3 300 V电力电子应用的候选器件。基于此,回顾了垂直结构氮化镓晶体管的最新进展,特别是与器件相关的材料和工艺问题,并总结了开发高性能垂直结构氮化镓功率晶体管的主要挑战。     

GaN Substrates—Progress, Status, and Prospects

Recent advances in the research, development, and commercial production of native GaN substrates with low defect density and high structural and optical quality have attracted a renewed interest in development of nitride devices based on native substrates. The still low yet rapidly increasing availability of native GaN substrates opens the full potential of GaN devices and has accelerated progress in the development of several electronic and optoelectronic devices. In this paper, progress in the primary competing growth techniques for producing native GaN substrates will be reviewed. The technological issues pertaining to faster scalability of GaN substrate production will be discussed. The current state-of-the-art substrate material properties and the future prospects for the growth approaches and substrate quality will be presented.      

六英寸Si基GaN功率电子材料及器件的制备与研究

氮化镓(GaN)作为第三代半导体材料的代表,具有优异的材料物理特性,更加适合于下一代电力电子系统对功率开关器件更大功率、更高频率、更小体积和更恶劣工作温度的要求。为了兼容Si基CMOS工艺流程,以及考虑到大尺寸、低成本等优势,在Si衬底上进行GaN材料的异质外延及器件制备已经成为业界主要技术路线。详细介绍了在6英寸Si衬底上外延生长的AlGaN/GaN HEMT结构功率电子材料,以及基于6英寸CMOS产线制造Si基GaN功率MIS-HEMT和常关型Cascode GaN器件的相关成果。     

Advanced Power Module Packaging and Integration Structures for High Frequency Power Conversion:From Silicon to GaN

The emerging of commercial high-voltage gallium nitride(GaN) power devices provides extraordinary switching performance over silicone devices, which enables high-voltage power conversion switching at megahertz range.Such outstanding features also pose strong challenges for device packaging design since the package parasitics can significantly influence the device switching characteristics, and thus can shadow the advantages brought by GaN devices. Designers have been dealing with these challenges brought by high du/dt and high-frequency switching operation even since the silicon(Si) era when fast switching Si MOSFET is first developed and came up with lots of inspiring advanced power module packaging structures to mitigate the problems.This paper presents a review of advanced power module packaging and integration structures that are suitable for high frequency power conversion.The review covers the heritage from the high frequency Si MOSFET packaging to the state-of-the-art for GaN devices.     

第三代半导体GaN功率开关器件的发展现状及面临的挑战

氮化镓(GaN)材料具有优异的物理特性,非常适合于制作高温、高速和大功率电子器件,具有十分广阔的市场前景。Si衬底上GaN基功率开关器件是目前的主流技术路线,其中结型栅结构(p型栅)和共源共栅级联结构(Cascode)的常关型器件已经逐步实现产业化,并在通用电源及光伏逆变等领域得到应用。但是鉴于以上两种器件结构存在的缺点,业界更加期待能更充分发挥GaN性能的"真"常关MOSFET器件。而GaN MOSFET器件的全面实用化,仍然面临着在材料外延方面和器件稳定性方面的挑战。     

基于GaN器件的固态射频电源应用研究

随着电力电子技术的发展,射频电源由电子管电源发展成现在的晶体管射频电源。氮化镓GaN(gallium nitride)作为第三代宽禁带半导体材料的典型代表,具有宽禁带、高临界击穿场强、高电子饱和漂移速度以及高导通的AlGaN/GaN异质结二维电子气2DEG(two-dimensional electrons gas)等优点。GaN功率器件与硅(Si)功率器件相比,具有导通阻抗低,输入、输出电容小等特性,这些特性使得GaN功率器件高开关速度、低损耗。在E类功率射频电源的基础上,采用GaN功率器件设计制作了一款开关频率为4 MHz、功率可调的全固态射频电源实验样机。通过电路的设计和优化,样机的输出功率为21.4 W时,效率达到了96.7%;同时,采用专为射频电源生产的Si功率器件替换掉样机上的GaN器件,实验数据验证了GaN器件开关速度快、损耗低,可大幅度提高射频电源的效率。     

基于GaN FETs的高频半桥谐振变换器分析与设计

随着Si材料半导体器件性能逐步达到瓶颈,宽禁带半导体器件(GaN、SiC)在诸多方面展现出了很好的性能,如低导通阻抗,小输入、输出电容等,这些特性使得GaN和SiC器件能够应用在更高的开关频率条件,从而提高系统的功率密度。针对基于GaN FETs构成的高频半桥谐振变换器进行设计,分析了高频条件下寄生电感参数对系统驱动电压及漏源极电压的影响,同时分析了高频条件下系统电压电流测量所需注意的事项及影响因素,为高频条件下GaN FETs的应用提供一定的帮助。     

GaN高电子迁移率晶体管的研究进展

GaN高电子迁移率晶体管(HEMT)是GaN微波功率器件的主要形式,是第3代半导体技术领域发展和竞争的焦点.针对GaN HEMT的目标特性和电流崩塌现象,从材料结构设计和器件设计两方面概括了十几年来GaN HEMT器件性能优化的研究方法,并给出了国内外GaN HEMT器件微波功率特性目前的研究进展水平.     

碳化硅器件的短路保护：设计准则和电路

为了保障碳化硅(silicon carbide,Si C)在发生短路故障时可安全可靠的关断,需在掌握其短路特性基本规律的前提下,针对Si C短路耐受时间较短、短路下器件漏源极电压拐点不明显等特征,展开去饱和保护电路(desaturation fault protection,DESAT)电路中关键参数的研究,并制定其工程化设计的参考标准。在此基础上,文中进一步提出基于氮化镓(galliumnitride,GaN)的高速、低传输延时的DESAT短路保护电路,短路保护电路的驱动动作延时仅为常规基于硅器件DESAT电路的23.2%。所提出的氮化镓DESAT电路为SiC MOSFET短路保护电路的更优越的实现方案。     

宽禁带器件应用技术专辑主编评述

近20年来,以碳化硅和氮化镓为代表的宽禁带半导体功率器件具有电气性能和热性能等方面的优势,正在成为硅器件的强力替代品。业界成功研制出SiC MOSFET、GaN HEMT等先进器件,已在能源汽车、轨道交通、能源互联等行业展示出高开关能力和高温能力。基于功率器件设计、封装、实验方法、栅极驱动等方面的最新研究进展,《电源学报》特别推出"宽禁带器件应用技术"专辑,以期推进宽禁带器件前沿技术与应用难点和热点问题的探讨。     

Metalorganic Vapor Phase Epitaxy of III-Nitride Light-Emitting Diodes on Nanopatterned AGOG Sapphire Substrate by Abbreviated Growth Mode

Metalorganic vapor phase epitaxial (MOVPE) growth of GaN on nanopatterned AGOG sapphire substrates was performed, and characteristics of the light-emitting diode (LED) devices grown on patterned sapphire and planar substrates were compared. The nanopatterned sapphire substrates were fabricated by a novel process (AGOG) whereby aluminum nanomesas were epitaxially converted into crystalline $hbox{Al}_{2}hbox{O}_{3}$ via a two-stage annealing process. The GaN template grown on the nanopatterned sapphire substrate was done via an abbreviated growth mode, where a 15-nm thick, low-temperature GaN buffer layer was used, without the use of an etch-back and recovery process during the epitaxy. InGaN quantum wells (QWs) LEDs were grown on the GaN template on the nanopatterned sapphire, employing the abbreviated growth mode. The optimized InGaN QW LEDs grown on the patterned AGOG sapphire substrate exhibited a 24% improvement in output power as compared to LEDs on GaN templates grown using the conventional method. The increase in output power of the LEDs is attributed to improved internal quantum efficiency of the LEDs.      

基于GaN器件的高速直流无刷电机驱动器

传统直流无刷电机(BLDCM)驱动器以硅晶体管作为功率器件,工作频率低、开关损耗大,不适用于高速应用场合。宽禁带半导体氮化镓(GaN)晶体管,具有开关速度快、导通电阻小等优势,是高速驱动器的理想选择之一。基于GaN器件,设计了一款20 000 r/min转速的高速BLDCM驱动器。首先介绍了BLDCM驱动的工作原理,然后分析了GaN器件晶体管栅极驱动电阻值的计算过程,选取Si8273作为GaN晶体管GS61008P的驱动芯片,利用霍尔信号配合数字控制器软件得到换相脉冲,以完成高速驱动器的软硬件设计。验结果表明,GaN方案显著减小了驱动器体积,提高了响应速度。     

SiC Lateral Devices on Semi-insulating Substrate

The advancements in the technology development for silicon carbide(SiC) lateral devices are summarized in the past years.By replacing conducting substrates in the conventional devices with semi-insulating ones and by considering the charge compensation in the drift layer based on superjunction principle, blocking voltage can be enhanced by more than two times compared with those values reported in the literature.SiC lateral PiN diodes,JFETs,MOSFETs and IGBTs are realized with blocking voltages as high as 4.2 kV.A COMS inverter is also demonstrated at the sametime with the process of high-voltage lateral IGBTs, showing the potential for future SiC power management integrated circuits(ICs).     

宽禁带器件在1kV高频直流谐振变换器中的应用与对比

与传统硅Si(silicon)功率器件相比,第3代宽禁带功率半导体器件,如碳化硅SiC(silicon carbide)和氮化镓GaN(gallium nitride)功率器件,由于具有高功率密度、耐高温和抗辐照等特点,得到了越来越广泛的应用。分析了基于SiC和GaN的2种1 kV输入、32 V/3 kW输出的LLC谐振变换器,通过仿真和实验探究了变压器匝间电容对谐振电流的影响;并采取分离谐振腔、改变变压器绕组结构的方法,减小谐振电流的畸变,保证了开关管ZVS的实现。由于大匝比变压器难以平面化,2种变换器均采用原边串联、副边并联的矩阵变压器,实现自动均压、均流,降低电压和电流应力,提高功率密度和热稳定性。为了进一步提高效率,GaN LLC变换器副边采用同步整流。最后,本文从拓扑、损耗、整机尺寸、可靠性以及功率密度等方面对比分析了这2种变换器的优缺点,为器件的选择提供了参考依据。     

半导体GaN功率开关器件灵敏度测试技术

测试半导体GaN功率开关器件灵敏度对掌握器件性能具有重要意义,提出一种新的半导体GaN功率开关器件灵敏度测试技术。通过分析半导体GaN功率开关器件的导通电阻与击穿电压关系、空穴电流与栅极电流关系掌握功率开关器件击穿机理,在此基础上,测试半导体GaN功率开关器件灵敏度;根据灵敏度测试原理与微频通道衰减值周期检查原理,测量功率开关器件微频信号功率和微频通道衰减值,汇总微频通道衰减值和最后一次开关灵敏时的衰减值,得到半导体GaN功率开关器件灵敏度。实验结果表明：所提测试技术测量半导体GaN功率开关器件灵敏度过程中,平均测试误差为0.03 dB,仅平均花费9.42ms,是一种高效、可靠的半导体GaN功率开关器件灵敏度测试技术。     

GaN功率器件预驱动芯片设计与封装集成

氮化镓GaN(gallium nitride)功率器件因其出色的导通与开关特性,能够实现系统高频化与小型化,有效提升系统功率密度。但是,增强型GaN功率器件由于其栅极可靠性问题,使其在电源管理系统中无法直接替换传统硅基功率MOSFET器件。为此,提出一种预驱动芯片,通过片内集成LDO与电平移位结构,实现兼容12～15 V输入,并输出5 V信号对GaN功率器件的栅极进行有效与可靠控制,达到兼容传统硅基功率器件应用系统的要求。此外,通过多芯片合封技术,将预驱动芯片与GaN功率器件实现封装集成,降低了寄生电感,使其应用可靠性进一步提升。     

Si IGBT/SiC MOSFET混合器件及其应用研究

综述了Si IGBT/SiC MOSFET混合器件在门极优化控制策略、集成驱动设计、热电耦合损耗模型、芯片尺寸配比优化和混合功率模块研制等方面的最新研究成果与进展。Si IGBT/SiC MOSFET混合器件结合了SiC MOSFET的高开关频率、低开关损耗特性和Si IGBT的大载流能力和低成本优势,已有文献的最新研究和实验结果验证了该类器件的优异特性,表明其对高性能电力电子器件实现更高电流容量、更高开关频率和较低成本具有重要意义,是高性能变换器应用中非常有潜力的功率器件类型。     

Focused ion beam-based fabrication of nanostructured photonic devices

This paper presents results for focused ion beam (FIB) processing of two photonic devices: 1) a GaN laser with a fourth-order grating for vertical emission, and 2) a two-dimensional (2-D) photonic crystal (PhC) structure. For the GaN laser, both L-I and I-V results are shown before and after etching, and vertical emitted power as a function of the distance along grating is shown. A finite element (FE)-based electromagnetic model is developed to support the measured results and is used to predict the optimum grating depth. For the 2-D photonic crystal, direct FIB etching is used to create a PhC in a standard InP waveguide structure. Measured and modeled transmission results are compared, and there is good agreement for band edge position. A detailed study of hole shape is presented, and this leads to the development of a multistage etching procedure involving both reactive ion etching and inductively coupled plasma etching. This results in a much improved hole shape.     

Semi-analytical modeling of Ag and Au nanoparticles and fullerene (C60) embedded gate oxide compound semiconductor MOSFET memory devices

In this paper we present an analytical simulation study of Non-volatile MOSFET memory devices with Ag/Au nanoparticles/fullerene (C60) embedded gate dielectric stacks. We considered a long channel planar MOSFET, having a multilayer SiO₂–HfO₂ (7.5?nm)–Ag/Au nc/C60 embedded HfO₂ (6?nm)–HfO₂ (30?nm) gate dielectric stack. We considered three substrate materials GaN, InP and the conventional Si substrate, for use in such MOSFET NVM devices. From a semi-analytic solution of the Poisson equation, the potential and the electric fields in the substrate and the different layers of the gate oxide stack were derived. Thereafter using the WKB approximation, we have investigated the Fowler-Nordheim tunneling currents from the Si inversion layer to the embedded nanocrystal states in such devices. From our model, we simulated the write-erase characteristics, gate tunneling currents, and the transient threshold voltage shifts of the MOSFET NVM devices. The results from our model were compared with recent experimental results for Au nc and Ag nc embedded gate dielectric MOSFET memories. From the studies, the C60 embedded devices showed faster charging performance and higher charge storage, than both the metallic nc embedded devices. The nc Au embedded device displayed superior characteristics compared to the nc Ag embedded device. From the model GaN emerged as the overall better substrate material than Si and InP in terms of higher threshold voltage shift, lesser write programming voltage and better charge retention capabilities.