GaN HEMT器件热特性的电学测试法

基于JEDEC颁布的结到壳热阻瞬态热测试界面法,对测试GaN HEMT器件热特性的电学法进行了研究.通过合理的测试电路设计,有效解决了GaN HEMT器件电学法测试中的栅极保护问题和自激问题,实现了GaN HEMT器件的界面热阻测量.根据测得的热阻-热容结构函数曲线可知,GaN HEMT器件结到壳热阻主要由金锡焊接工艺和管壳热特性决定.结合结构函数分析,对金锡焊接部分热阻和管壳热阻进行排序可剔除有工艺缺陷的器件.与红外热成像法的结温测试结果进行对比分析,证实了电学法测试结果的准确性.     

结温准确性对GaN HEMT加速寿命评估的影响

通过对阿伦尼斯方程进行研究,指出了结温检测结果的误差将会影响加速寿命试验结果的准确性.根据GaN HEMT加速寿命试验中常用的结温获取方式,分别讨论了采用热阻修正结温和直接测量结温两种方式获取结温对器件寿命评估结果造成的影响.研究了Cree公司GaN HEMT结温测量方法,指出依据显微红外测温结果得到的加速寿命数据与依据有限元仿真得到的加速寿命数据相差近4倍.     

GaN基HEMT器件的优化设计北大核心CSCD

针对氮化镓(GaN)高电子迁移率晶体管(HEMT)器件自热效应以及电流崩塌效应导致器件性能退化和失效的问题,研究了通过合理改变器件参数尺寸优化GaN基HEMT器件的设计,提高器件性能。通过仿真软件模拟了器件各参数对于GaN器件电学性能的影响,分析了不同衬底构成对GaN HEMT器件自热效应的影响,系统研究了GaN HEMT器件相关参数改变对自热效应及器件电学性能的影响。结果表明:Si及金刚石组成的衬底中减小Si层的厚度有利于减小器件的自热效应,降低有源区最高温度。为提高器件性能以及进一步优化GaN基HEMT器件设计提供了一定的理论参考。     

GaN基HEMT器件的优化设计

针对氮化镓(GaN)高电子迁移率晶体管(HEMT)器件自热效应以及电流崩塌效应导致器件性能退化和失效的问题,研究了通过合理改变器件参数尺寸优化GaN基HEMT器件的设计,提高器件性能。通过仿真软件模拟了器件各参数对于GaN器件电学性能的影响,分析了不同衬底构成对GaN HEMT器件自热效应的影响,系统研究了GaN HEMT器件相关参数改变对自热效应及器件电学性能的影响。结果表明:Si及金刚石组成的衬底中减小Si层的厚度有利于减小器件的自热效应,降低有源区最高温度。为提高器件性能以及进一步优化GaN基HEMT器件设计提供了一定的理论参考。     

毫米波GaN基HEMT器件材料结构发展的研究

由于GaN材料的高的饱和电子速度和击穿场强,GaN基HEMT已经成为实现毫米波器件的重要选择。回顾了GaN基HEMT器件材料结构的发展历程,就目前GaN基毫米波HEMT器件设计应用存在的短沟道效应和源漏间较大的导通电阻两个主要问题进行了机理分析,并对GaN基HEMT器件的毫米波应用未来发展方向进行了分析。同时从GaN基HEMT器件材料结构设计入手对解决方案进行了探讨性研究。针对面向毫米波应用的GaN基HEMT材料结构,为有效的抑制短沟道效应,可以采用栅凹槽结构加背势垒结构、采用InAlN等新材料,可以有效降低源漏导通电阻。     

场板结构对AlGaN/GaN HEMT温度场的影响北大核心CSCD

用Silvaco的ATLAS软件仿真研究了场板结构对AlGaN/GaN高电子迁移率晶体管(HEMT)的温度场分布的影响,分析了场板结构影响器件温度场分布的可能因素。模拟结果表明,加入场板结构后,器件沟道二维电子气浓度减小,电场分布发生变化,器件栅极漏侧边缘处的沟道峰值温度降低。加入栅场板和源场板结构后,场板边缘处都有一个新的温度峰值出现,器件的沟道温度峰值在加入单层和双层栅场板及源场板后由511K分别下降到487、468和484K,这种降低作用会随着栅场板层数的增加而有所增强。仿真结果说明场板结构通过改变AlGaN/GaN HEMT器件沟道载流子浓度和电场分布,影响器件内部的温度场分布。优化器件的场板结构是提高AlGaN/GaN HEMT的可靠性有效途径之一。     

AlGaN/GaN高电子迁移率晶体管的可靠性

利用正向肖特基结结电压与温度的线性关系,对AlGaN/GaN HEMT器件有源区瞬态温升进行了测量,其热阻为19.6℃/W。比较了不同测温方法和外界环境对器件沟道温升的影响。并研究了栅极施加反向直流阶梯应力对AlGaN/GaN HEMT器件性能的影响,结果表明器件在应力作用下电学参数退化,大信号寄生源/漏极电阻RS/RD和栅源正向I-V特性在击穿后能得到恢复。AlGaN势垒层陷阱俘获电子和电子填充栅极表面态是器件参数退化的原因,表面态恢复是器件参数恢复的主要原因。     

AlN阻挡层对AlGaN/GaNHEMT器件的影响

利用低压MOCVD技术在蓝宝石衬底上生长了AlGaN/GaN异质结和AlGaN/AlN/GaN异质结二维电子气材料,采用相同器件工艺制造出了AlGaN/GaN HEMT器件和AlGaN/AlN/GaN HEMT器件.通过对两种不同器件的比较和讨论,研究了AlN阻挡层的增加对AlGaN/GaN HEMT器件性能的影响.     

毫米波AlGaN / GaN HEMT 交流特性研究

毫米波频段已经成为AlGaN/GaN HEMT研究的一个发展趋势。利用器件仿真软件TCAD,对AlGaN/GaN HEMT交流特性进行了研究。从势垒层的Al组分和厚度两个参数分析了器件特征频率变化趋势。用TCAD仿真得到的AlGaN/GaN HEMT器件本征S参数,在ADS中添加器件的非本征参数,得到器件仿真的频率特性。在器件设计的基础上,进行了器件版图设计和流片,并测量了器件频率特性。测试和仿真结果的对比表明两者较为一致,表明器件仿真的有效性和指导意义。     

一种新的AlGaN/GaN HEMT半经验直流特性模型

在EEHEMT1模型的基础上给出一种新的A1GaN/GaN HEMT半经验直流特性模型,考虑了栅源电压对膝点电压的影响,得到描述AlGaN/GaN HEMT器件I-Ⅴ特性的方程.此模型可以应用于蓝宝石和SiC两种不同衬底AlGaN/GaN HEMT器件的I-Ⅴ特性模拟.仿真结果和实验测量结果拟合误差小于3%.     

Thermal evaluation of GaN-based HEMTs with various layer sizes and structural parameters using finite-element thermal simulation

By using scanning electron microscopy (SEM) and infrared data, we established and verified a two-dimensional finite-element model conforming to the size of the practical device to study high-electron-mobility transistors (HEMTs). Because the resolution of the infrared measurement was 7 μm, we verified the correctness of the model by comparing the 7-μm average peak temperature with the measured infrared data at various platform temperatures. The simulated average peak temperature agrees well with the infrared data. To further investigate the thermal performance of GaN-based HEMTs with various layer sizes and structural parameters, we simulated devices with various values of gate length, gate spacing, GaN layer thickness, substrate breadth, and substrate thickness. The conclusions presented result from some factors that must be taken into account to manage thermal issues in devices.     

GaN HEMT器件稳态热特性试验研究

大功率GaN HEMT器件在工作时较高的热流密度引发器件高温,而高温会显著影响器件性能及可靠性。从不同器件结构设计出发,结合器件热量传递理论,建立了器件热阻模型;采用高速红外热像仪试验分析了器件结构对GaN HEMT器件稳态热特性的影响,定量给出了不同总栅宽、不同单指栅宽、不同栅间距在不同功率密度下的稳态温升。相关结果可用于研发阶段器件结温的快速评估。     

一种紧凑的GaN高电子迁移率晶体管大信号模型拓扑

GaN高电子迁移率晶体管（HEMT）以其复杂的器件特性使其大信号建模变得十分困难,尽管EEHEMT、Angelov等模型结构曾经成功应用于GaAs HEMT/MESFET的大信号模型,但当它们被用于GaN HEMT建模时却不再准确和完备.面向GaN HEMT器件的大信号模型,本文提出了一种紧凑的模型拓扑,此模型拓扑综合了GaN HEMT器件的直流电压-电流（I-V）特性、非线性电容、寄生参数、栅延迟漏延迟与电流崩塌、自热效应以及噪声等特性.经验证此模型拓扑在仿真中具有很好的收敛性,适用于GaN HEMT器件的大信号模型的建立,满足GaN基微波电路设计对器件模型的需求.     

热源尺寸对AlGaN/GaN HEMT器件热阻的影响机理

基于CREE公司生产的十条栅指AlGaN/GaN HEMT器件,利用热传导方程,研究了AlGaN/GaN HEMT器件热阻随热源尺寸的变化规律及影响机理,建立了GaN HEMT器件的热传播模型并通过红外测温法结合Sentaurus TCAD模拟仿真的方法验证了模型的准确性.研究发现:热阻随热源尺寸的减小以近似指数的规律增加,随栅宽的减小以反比的规律增加.另外,在芯片尺寸、散热条件、功率密度等条件不变的情况下,栅长从1μm减小到0.05μm时,热阻大约增加80％.对该变化规律从两个方面进行了解释:一方面,热源面积越小,微观尺寸上的散热面积越小,热阻越大;另外,热源尺寸的减小会引起热源处热容的减小,产生的热量是一定的,热阻与温升成正比,因此对应的热阻增加.     

Physical study of the dissipated power area in high electron mobility transistors for thermal modelling

The hot area in power transistors due to the power dissipation is determined from a 2D-hydrodynamic model. The power is calculated everywhere in the device from the knowledge of the physical quantities (current density, electric field). The hot area is determined accurately to be coupled to a thermal modelling giving the temperature everywhere in the device [J. Park, M.-W Shin, C.-C. Lee, Thermal modeling and measurement of GaN-based HFET devices, IEEE Electron Device Lett. 24(7) (2003) 424-426 [1]; J.-C Jacquet, R. Aubry, H. Gérard, E. Delos, N. Rolland, Y. Cordier, A. Bussutil, M. Rousseau, S.L. Delage, Analytical transport model of AlGaN/GaN HEMT based on electrical and thermal measurement, 12th GAAS Symposium, Amsterdam, 2004, pp. 235-238 [2].]. The method is applied to HEMTs (high electron mobility transistors) based on GaAs or GaN. It is shown that the hot area depends on the bias conditions and on the transistor gate recess topology.     

LED背光模组热管理研究

文章建立了RGB三合一LED背光模组的热分析模型,通过与红外热像仪实际测量得到的温度数据相互比较,验证了该模型仿真结果的准确性。模拟分析的结果表明,在LED阵列底部固定一块镀锌钢板可有效降低LED结温。文章还提出了一种利用最小二乘法原理推算LED结点温度的方法,得到了电路板表面温度与LED结温之间的关系式,有助于通过测量电路板温度估算LED的结点温度,并以此为根据对LED进行亮度和色度的调节。     

Thermal modeling and measurement of GaN-based HFET devices

In this letter, we present our thermal study results of GaN-based heterojunction field effect transistors (HFETs). In thermal computation, PAMICE code was used to calculate temperatures in a three-dimension (3-D) model. In the thermal measurement, nematic liquid crystal thermography was employed to determine the peak temperature on the surface of the device chip. The calculated and directly measured temperatures agree well. These methods are valuable in predicting the thermal performance of GaN-based HFET devices, in particular the power devices.     

Nonlinear characterization of GaN HEMT

DC I-V output, small signal and an extensive large signal characterization (load-pull measurements) of a GaN HEMT on a SiC substrate with different gate widths of 100μm and 1 mm have been carried out. From the small signal data, it has been found that the cutoff frequencies increase with gate width varying from 100μm to 1 mm, owing to the reduced contribution of the parasitic effect. The devices investigated with different gate widths are enough to work in the C band and X band. The large signal measurements include the load-pull measurements and power sweep measurements at the C band (5.5 GHz) and X band (8 GHz). When biasing the gate voltage in class AB and selecting the source impedance, the optimum load impedances seen from the device for output power and PAE were localized in the load-pull map. The results of a power sweep at an 8 GHz biased various drain voltage demonstrate that a GaN HEMT on a SiC substrate has good thermal conductivity and a high breakdown voltage, and the CW power density of 10.16 W/mm was obtained. From the results of the power sweep measurement at 5.5 GHz with different gate widths, the actual scaling rules and heat effect on the large periphery device were analyzed, although the effects are not serious.The measurement results and analyses prove that a GaN HEMT on a SiC substrate is an ideal candidate for high-power amplifier design.     

0.15 μm passivated InP-based HEMT MMIC technology with highthermal stability in hydrogen ambient

The effect of thermal stress on InP-based HEMT MMIC with Ti-Pt-Au gate metallization in N₂ and H₂ forming gas is reported. The importance of stabilization bake at high temperature under nitrogen to stabilize the threshold voltage and device parameters is demonstrated. In addition, through thermal stress at 270°C with hydrogen ambient, we found, that our InP based HEMT devices and MMICs with Ti-Pt-Au gate metallization are not sensitive to hydrogen. To our knowledge, this is the first demonstration of hydrogen insensitive FET's and MMIC's with Ti-Pt-Au gate metallization