GaN基HFET电力电子器件的研究

作为第三代宽禁带半导体器件,GaN基HFET功率器件具耐高压、高频、导通电阻小等优良特性,在电力电子器件方面也具有卓越的优势。概述了基于电力电子方面应用的AlGaN/GaN HFET功率器件的研究进展。从器件的结构入手,介绍了AlGaN/GaN HEMT的研究现状,从栅材料的选取以及栅介质层的结构对器件性能的影响着手,对AlGaN/GaN MIS-HFET的研究进行了详细的介绍。分析了场板改善器件击穿特性的原理以及各种场板结构AlGaN/GaNHFET器件的研究进展。论述了实现增强型器件不同的方法。阐述了GaN基HFET功率器件在材料、器件结构、稳定性、工艺等方面所面临的挑战。最后探讨了GaN基HFET功率器件未来的发展趋势。     

英飞凌将与松下电器联袂推出常闭型600V GaN功率器件

2015年3月20日,英飞凌科技股份公司和松下电器公司宣布,两家公司已达成协议,将联合开发采用松下电器的常闭式(增强型)硅基氮化镓(Ga N)晶体管结构,与英飞凌的表贴(SMD)封装的Ga N器件。在此背景下,松下电器向英飞凌授予了使用其常闭型Ga N晶体管结构的许可。按照这份协议的规定,两家公司均可生产高性能Ga N器件。由此带来的益处是客户可以从两条渠道获得采用可兼容封装的     

安森美半导体加入imec的硅基氮化镓研究项目

正应用于高能效电子产品的首要高性能硅方案供应商安森美半导体(ONSemiconductor)加入了领先纳米电子研究中心imec的多合作伙伴业界研究及开发项目,共同开发下一代硅基氮化镓(GaN-on-Si)功率器件。氮化镓具有优异电子迁移率、更高击穿电压及良好导热性的特性,使其非常适合于要求高开关能效的功率器件及射频(RF)器件。如今,基于氮化镓的功     

氮化镓HEMT器件辐射效应综述

在高频、大功率、高温、高压等领域,氮化镓高电子迁移率晶体管(HEMT)器件因其优异的耐辐射性能而被广泛地应用于卫星、太空探测、核反应堆等领域。尽管从理论和一些试验研究中可以得知,氮化镓材料具有良好的耐辐射特性,但在实际应用中,因其制作工艺及结构等因素的影响,氮化镓HEMT器件的耐辐射特性受到了很大的影响和挑战。本文介绍了氮化镓HEMT器件几种辐射效应,并对氮化镓HEMT器件辐射的研究进行了综述。     

激光剥离GaN表面的抛光技术

激光剥离(LLO)技术是研制新型氮化镓(GaN)基谐振腔结构光电子器件的关键技术。然而LLO后的GaN表面往往具有较大的粗糙度,而制作谐振腔结构器件需要很高的表面平整度,因此需要对LLO后的GaN表面进行抛光。分别采用金刚石粉抛光液和胶粒二氧化硅抛光液进行机械抛光和化学机械抛光(CMP),并对比了两种方法获得的抛光结果,研究发现前者会在抛光后的GaN表面引入划痕,而采用后者可以得到亚纳米级平整度的表面。进一步的实验结果表明,胶粒二氧化硅抛光液同样适用于图形化衬底外延片激光剥离后的GaN表面抛光。     

富士通半导体明年计划量产氮化镓功率器件满足高效电源单元供应市场需求

满足高效电源单元供应市场需求富士通半导体(上海)有限公司宣布采用其基于硅基板的氮化镓(GaN)功率器件的服务器电源单元成功实现2.5 kW的高输出功率,富士通半导体计划将于2013年下半年开始量产这些GaN功率器件。这些器件可广泛用于电源增值应用,对实现低碳社会做出重大贡献。     

基于蓝绿光Micro-LED的可见光通信芯片调制带宽研究

基于氮化镓微米LED(Micro-LED)的可见光通信(Visible Light Communication,VLC)技术成为近年来的研究热点.通过深紫外光刻技术制备了小尺寸的氮化镓基蓝/绿光Micro-LED芯片,深入研究了40～10μm不同尺寸Micro-LED器件的性能,以及其作为VLC光源的调制带宽能力.研究发现,随着LED器件尺寸的缩小,其调制带宽显著增加.通过在电极间加入电磁屏障以及对LED器件侧壁进行钝化修复,直径为10 μm的绿光Micro-LED亮度可达1×108 cd/m2,直径为20 μm的蓝光Micro-LED的调制带宽可达372.6 MHz.研究结果表明,基于氮化镓的Micro-LED芯片在调制带宽上仍有较大的提升空间,经过进一步的研究,有望推动高速可见光通信的系统应用.     

AlGaN器件欧姆接触的研究进展

作为制备光电子器件例如紫外光子探测器、异质结场效应晶体管(HFET)、高电子迁移率晶体管(HEMT)异质结场效应管等的一种宽禁带半导体材料, III V 族氮化物AlGaN器件近年来颇受关注.AlGaN与金属之间的低阻欧姆接触的实现问题阻碍了AlGaN(基)器件的发展.通过对相关文献的归纳分析,介绍了近年来AlGaN器件在欧姆接触形成、金属化方案、合金化工艺及表面处理等方面的研究进展.     

AlGaN/GaN异质结场效应晶体管的阈值电压

利用AlGaN/GaN异质结场效应晶体管(AlGaN/GaN HFET)栅结构的电容-电压(C-V)特性确定AlGaN/GaN HFET的阈值电压.通过对模拟计算得到的AlGaN/GaN HFET电流-电压(I-V)特性曲线与测试得到的AlGaN/GaN HFET曲线比较分析,证实了依据AlGaN/GaN HFET栅结构的C-V特性曲线的微分极值点确定阈值电压是一种切实可行的方法.     

AlGaN/GaN异质结场效应晶体管的阈值电压

利用AlGaN/GaN异质结场效应晶体管(AlGaN/GaN HFET)栅结构的电容-电压(C-V)特性确定AlGaN/GaN HFET的阈值电压.通过对模拟计算得到的AlGaN/GaN HFET电流-电压(I-V)特性曲线与测试得到的AlGaN/GaN HFET曲线比较分析,证实了依据AlGaN/GaN HFET栅结构的C-V特性曲线的微分极值点确定阈值电压是一种切实可行的方法.     

Experimental and theoretical examination of orientation effect on piezoelectric charge at gate periphery in AlGaN/GaN HFETs

Orientation effect on AlGaN/GaN heterojunction field-effect transistors (HFETs) has been experimentally and theoretically examined in detail. The drain-currents of the fabricated AlGaN/GaN HFETs with various gate directions do not depend on the gate orientation, whereas those of GaAs-based HFETs strongly depend on the gate direction due to the piezoelectric charges induced around the gate electrode. The piezoelectric charges induced in the vicinity of the gate electrode are simulated by using a finite-element method. This simulation solves the piezoelectric equations with piezoelectric and elastic stiffness constants, assuming that stress is applied to the gate edges in the HFET. The detailed simulation reveals that the piezoelectric charge distribution does not depend on the gate direction, although a large amount of piezoelectric charges is induced in the vicinity of the gate edges, which is consistent with the experimental result. Moreover, it is mathematically clarified that these experimental and simulated results are due to the symmetry characteristic of the piezoelectric and elastic stiffness constants for nitride semiconductor materials.     

Switching Characteristics of GaN HFETs in a Half Bridge Package for High Temperature Applications

AlGaN/GaN heterojunction field effect transistors (HFETs) are expected to be a good candidate for power switching application at high temperatures. We designed and fabricated a discrete HFET package and a half bridge module using the AlGaN/GaN HFETs and SiC Schottky barrier diodes (SBDs) for high temperature applications. The half bridge module exhibited good reliability after 250 C and 400 h high temperature storage. Switching characteristics of the AlGaN/GaN HFET were investigated. Qg x Ron, which shows a figure of merit of switching operation, was more than 10 times better than commercial Si MOSFETs. The switching characteristics of the HFET showed no significant degradation up to 225 C.     

AlGaN/GaN MIS-HFETs with f/sub T/ of 163 GHz using cat-CVD SiN gate-insulating and passivation Layers

Al/sub 0.4/Ga/sub 0.6/N/GaN heterostructure field-effect transistors (HFETs) with an AlGaN barrier thickness of 8 nm and a gate length (L/sub G/) of 0.06-0.2 /spl mu/m were fabricated on a sapphire substrate. We employed two novel techniques, which were thin, high-Al-composition AlGaN barrier layers and SiN gate-insulating, passivation layers formed by catalytic chemical vapor deposition, to enhance high-frequency device characteristics by suppressing the short channel effect. The HFETs with L/sub G/=0.06-0.2 /spl mu/m had a maximum drain current density of 1.17-1.24 A/mm at a gate bias of +1.0 V and a peak extrinsic transconductance of 305-417 mS/mm. The current-gain cutoff frequency (f/sub T/) was 163 GHz, which is the highest value to have been reported for GaN HFETs. The maximum oscillation frequency (f/sub max/) was also high, and its value derived from the maximum stable gain or unilateral gain was 192 or 163 GHz, respectively.     

基于60 nm T型栅fT & fmax为170 & 210 GHz 的InAlN/GaN HFETs 器件

基于蓝宝石衬底InAlN/GaN异质结材料研制具有高电流增益截止频率(fT)和最大振荡频率(fmax)的InAlN/GaN异质结场效应晶体管 (HFETs)。基于再生长n GaN欧姆接触工艺实现了器件尺寸的缩小,有效源漏间距(Lsd)缩小至600 nm。此外,采用自对准栅工艺制备60 nm T型栅。由于器件尺寸的缩小,在Vgs= 1 V下,器件最大饱和电流(Ids)达到1.89 A/mm,峰值跨导达到462 mS/mm。根据小信号测试结果,外推得到器件的fT和fmax分别为170 GHz和210 GHz,该频率特性为国内InAlN/GaN HFETs器件频率的最高值。     

GaN HFET中的噪声

从GaN异质结沟道阱中电子状态出发研究了HFET中的噪声产生机理.用沟道阱中子带间散射解释了迁移率起伏引起的1/f噪声.从电子状态转移及不同状态间的跃迁出发解释了各类噪声实验结果.建立了沟道阱能带与HFET噪声性能间的关联.运用正、负极化电荷剪裁了肖特基势垒、欧姆接触及内、外沟道的势垒和主阱及副阱阱宽和势垒高度,降低了栅流、欧姆接触和外沟道串联电阻,强化了沟道阱的量子限制,减弱了子带间散射.     

Synthesis and characterization of p-type NiO films suitable for normally-off AlGaN/GaN HFETs application

p-type NiO films were prepared at different oxidizing temperatures in O₂ ambient for normally-off AlGaN/GaN HFETs application. The crystalline structure, electrical properties and band gap of NiO films are dependent upon temperatures. Compared with the conventional Ni-gated HFETs, NiO-gated HFETs present positively shifted threshold voltage and smaller gate leakage current, while the drain current density shows slightly degradation. Combining the recess structure and NiO gate, normally-off GaN HFETs was achieved with a threshold voltage of approximately 0.5 V. The band diagram of the NiO/AlGaN/GaN structure demonstrates that the p-type conductivity and large conduction band offset between NiO and GaN cause the lift-up potential, which result in 2DEG depletion and positive threshold voltage shift.     

Flicker noise of GaN-based heterostructure field-effect transistors with Si-doped AlGaN carrier injection layer

Aluminum gallium nitride/gallium nitride (AlGaN/GaN) heterostructure field effect transistors (HFETs) with and without Si-doped AlGaN layer were fabricated and investigated. HFETs with the Si-doped AlGaN carrier-injection layer show better DC performance, and the transconductance is 150 mS/mm. However, the HFETs with Si-doped AlGaN layer present the deviation from the 1/f noise at low frequency. The Lorentz shape was observed in the noise spectrum. It suggests that traps might be more pronounced in this kind of structure. Therefore, the DC characteristics of HFETs can be improved by the insertion of Si-doped AlGaN layer, but it can result in more low-frequency noise with the carrier-injection layer.     

SiC and GaN transistors - is there one winner for microwave power applications?

Wide bandgap semiconductors show promise for high-power microwave electronic devices. Primarily due to low breakdown voltage, it has not been possible to design and fabricate solid-state transistors that can yield radio-frequency (RF) output power on the order of hundreds to thousands of watts. This has severely limited their use in power applications. Recent improvements in the growth of wide bandgap semiconductor materials, such as SiC and the GaN-based alloys, provide the opportunity to now design and fabricate microwave transistors that demonstrate performance previously available only from microwave tubes. The most promising electronic devices for fabrication in wide bandgap semiconductors for these applications are metal-semiconductor field-effect transistors (MESFETs) fabricated from the 4H-SiC polytype and heterojunction field-effect transistors (HFETs) fabricated using the AlGaN/GaN heterojunction. These devices can provide RF output power on the order of 5-6 W/mm and 10-12 W/mm of gate periphery, respectively. 4H-SiC MESFETs should produce useful performance at least through X band and AlGaN/GaN HFETs should produce useful performance well into the millimeter-wave region, and potentially as high as 100 GHz.     

基于MOCVD再生长n+ GaN 欧姆接触工艺fT/fmax＞150/210 GHz的AlGaN/GaN HFETs器件研究

基于SiC衬底AlGaN/GaN异质结材料研制具有高电流增益截止频率(fT)和最大振荡频率(fmax)的AlGaN/GaN异质结场效应晶体管(HFETs).基于MOCVD外延n+ GaN 欧姆接触工艺实现了器件尺寸的缩小, 有效源漏间距(Lsd)缩小至600 nm.此外, 采用自对准工艺制备了60 nm T型栅.由于器件尺寸的缩小, 在Vgs=2 V下, 器件最大饱和电流(Ids)达到2.0 A/mm, 该值为AlGaN/GaN HFETs器件直流测试下的最高值, 器件峰值跨导达到608 mS/mm.小信号测试表明, 器件fT和fmax最高值分别达到152 GHz和219 GHz.     

基于再生长欧姆接触工艺的220 GHz InAlN/GaN 场效应晶体管

本文在蓝宝石衬底上研制了具有高电流增益截止频率(f_T)的InAlN/GaN异质结场效应晶体管 (HFETs)。基于MOCVD外延n -GaN欧姆接触工艺实现了器件尺寸的缩小,有效源漏间距(L_sd)缩小至600 nm。此外,采用自对准工艺制备了50 nm直栅。由于器件尺寸的缩小,V_gs= 1 V下器件最大饱和电流(I_ds)达到2.11 A/mm,峰值跨导达到609 mS/mm。小信号测试表明,器件f_T达到220 GHz、最大振荡频率(f_max)达到48 GHz。据我们所知,该f_T值是目前国内InAlN/GaN HFETs器件报道的最高结果。