【作者】 桑磊；

【导师】 徐锐敏；

【作者基本信息】 电子科技大学 ， 电磁场与微波技术， 2013， 博士

【摘要】 随着无线通信和雷达探测等领域的快速发展，现代电子设备对微波功率晶体管的工作频率和功率密度等方面的要求越来越高。与第一代和第二代半导体材料相比，以SiC和GaN为代表的宽禁带半导体材料，具有更高的耐压性能、更快的电子迁移率、更高的热导率以及更好的抗辐射性能，因此成为半导体器件研究的热点。其中，由于GaN功率器件具有更好的高频性能和更高的功率品质因子，使得它比SiC器件在高频大功率的应用上有着更为广阔的发展前景。目前，GaN功率器件的制备已经取得了一定进展，但其建模工作却相对滞后。GaN功率器件的模型在电路设计中起着关键性作用，模型的适用性和准确性对微波电路设计结果有着非常重要的影响。与传统功率器件相比，AlGaN/GaN HEMT在沟道形成和电流密度上都存在不小差异。目前的功率器件模型对其自热效应和非线性特性的描述还存在一定误差，这在一定程度上限制了GaN功率器件的发展。为加速GaN功率器件的应用，改进电路设计，促进GaN功率器件全面发展，急需对GaN功率器件进行建模研究。本文对AlGaN/GaN HEMT功率器件的关键特性进行了分析，围绕功率器件的经验基模型展开研究，改进了非线性等效电路模型；拓展了建立表格模型的思路；在X参数和Volterra级数的基础上，建立了功率器件的Volterra级数描述公式；并以等效电路模型为基础，设计了GaN高效率放大电路。具体研究内容包括：1. AlGaN/GaN HEMT功率器件等效电路模型针对AlGaN/GaN HEMT微波器件小信号等效电路参量多，数值提取复杂的特点，将待定系数法引入计算公式，配合优化软件，提高了小信号等效电路的预测精度。根据AlGaN/GaN HEMT微波器件电流电压曲线和芯片表面温度分布特性，以Angelov大信号模型为基础，对非线性电流和电容公式进行了改进，使新电流模型能够描述不同栅压时电流随漏压增加而上升或下降的趋势，反映温度对漏极电流的影响，预测了静态I-V曲线的自热效应和温度分布效应。并且将公式嵌入ADS软件中，形成完整的等效电路模型，对AlGaN/GaN HEMT功率器件的电流特性、频率特性和输出性能进行了仿真，与实测结果对比显示，新的大信号非线性模型可以提高预测结果的准确性。2. K最邻近算法为基础的AlGaN/GaN HEMT功率器件表格模型AlGaN/GaN HEMT功率器件的黑匣子表格模型无需考虑器件的内部结构和导电机理，可以用纯数学运算对器件进行建模和预测，因此能够充分运用数学方法，有效保护知识产权。但其建模过程需要大量测试数据，算法代码往往比较复杂。本文以漏极电流数据和S参数为基础，建立了非线性等效元件数据库，根据放大器的特点将K最邻近算法做了改进，建立了GaN HEMT功率器件表格模型，节约了建模数据，简化了模型结构，结合泰勒级数提取放大器的非线性元件数值，配合寄生元件和线性元件对输出特性进行计算，预测精度较高。3. X参数和Volterra级数为基础的AlGaN/GaN HEMT放大器模型X参数在频域内能够精确描述器件各个端口，每个频率分量之间的数值关系，但难以对器件时域特性进行描述。Volterra级数对器件的时域和频域特性描述都很准确，但提取过程太繁杂。本文将X参数和Volterra级数相结合，以AlGaN/GaNHEMT功率放大器的X参数为基础，提取Volterra核函数，得到时域和频域的Volterra级数模型，很好的描述和预测了放大器的时域和频域特性，节省了测试工作量，获得了较好的预测精度。4.以等效电路模型为基础的GaN HEMT高效率放大电路设计与测试以等效电路模型为基础，设计了一组AB类50W GaN功率放大电路和基于谐波调制技术的10W GaN功率放大电路，为了直观显示GaN HEMT功率器件的效率提升幅度，设计了相似功率量级的LDMOS功率放大电路。将电路仿真数据、GaN放大器和LDMOS放大器测试数据，以及近几年发表的GaAs pHEMT功率放大器测试数据进行比较分析，对比结果显示等效电路模型具有较好的预测效果，同时直观显示了GaN功率器件较传统功率器件的效率提升幅度。综上所述，改进的非线性电流公式和电容公式作为等效电路模型的核心，能够方便的嵌入主流微波仿真软件中，具有较好的适用性和预测准确度。在表格模型中引入KNN算法和用X参数提取Volterra级数的方法，拓宽了微波器件建模领域的思路，有望促进建模工作的进一步发展。更多还原

【Abstract】 With the development of wireless communication and radar exploration, modernelectronic equipment requires microwave power transistor with higher and higherfrequency and power density. In comparison with the first and second generationsemiconductor material, wide band gap semiconductor represented by SiC and GaN hasbetter voltage performance, faster electron drift mobility, higher conductivity and betterresistance of radioactive property. So the wide band gap semiconductor is focused onthe research of semiconductor device. Because of better frequency property and higherpower factor, GaN has wider development in the high frequency band and high powerapplication compared with SiC. Now, the manufacturing of GaN power device has madesome progress, but the model is relatively backward. The model of GaN power device isa very important factor in the design of microwave circuit, the applicability andaccuracy of the model has important effect in the design result. Compared withtraditional power device, AlGaN/GaN HEMT has a lot of difference in the channelformation and current density. The current power device model has some error in thecalculation of self-heating effect and nonlinear characteristics, which limits the overalldevelopment of GaN power device. In order to expedite the application of GaN powerdevice, improving the design of circuit, accelerating the development of GaN device,the model of GaN power device is instant needed. In this paper, the factorcharacteristics of AlGaN/GaN power device was analysed, and the research wascentered around on the experience model. The nonlinear equivalent circuit model wasimproved and the approach of establishing table model was broadened. Based on theX-parameters and Volterra series, the method of model was presented. According to theequivalent circuit model, high efficiency amplifier was designed. Following is thespecific research content:1. Equivalent circuit model of AlGaN/GaN HEMT power deviceSince the number of equivalent component is large and the extraction program iscomplex, the method of undetermined coefficients is used in the calculation programwith help of optimization software. The accuracy is improved. According to the curve of I-V, the formulas of nonlinear current and capacitance are improved which can describethe downward of current with the growth of voltage and the influence of the temperature.This description can reflect the effect of self-heating and temperature distribution. Theformulas are used in ADS software and based on which the current characteristics,frequency and output performance are calculated. Compared with measured data, theimproved nonlinear model can improve the accuracy of predication.2. Table model of AlGaN/GaN HEMT power device based on K nearestneighbors algorithmThe “black box” table model of AlGaN/GaN HEMT power device can neglect thestructure and conduct mechanism and use mathematics operation to model and predictpower device which could apply mathematics method adequately and protectintellectual property effectively. However, the model process needs a lot of measureddata and the algorithm code is always complicated. Based on the drain current andS-parameters data this research established table model of nonlinear equivalentcomponent in which the K nearest neighbors algorithm was improved. The model savesmeasured data and simplifies model structure. With help of Taylor series, nonlinearcomponents are extracted. The output performance is predicted and the accuracy isgood.3. Model of AlGaN/GaN HEMT power device based on X-parameters andVolterra seriesX-parameters can describe precisely the correlation coefficient between everyfrequency component in each port of power device. However, it can difficult reflect theperformance of device in time domain. Volterra series can describe the performance ofpower device in both time domain and frequency domain, but the extracting process istoo complex. X-parameters was conjunction with Volterra series in this research. Basedon X-parameters, kernel function of Volterra series was extracted easily with help ofwhich Volterra model can be used to predict the property of device in time domain andfrequency domain. The method which is a new idea for model can save measurementwork and get good accuracy.4. High effective GaN HEMT amplifier design and measurement based onequivalent circuit modelA class AB GaN power amplifier with50W output and a10W output power GaN amplifier were designed based on each equivalent circuit model. In order to quantizationanalysis the efficiency improvement, two LDMOS amplifier with similar output weredesigned and measured. The comparisons between prediction data, GaN amplifiermeasured data and LDMOS amplifier measured result show that the equivalent circuitmodel has a good accuracy and the GaN amplifier has a high efficiency.To sum up, the current formula in the equivalent circuit model presented in thispaper can be used in simulation software easily and has a good accuracy. The methodsof using KNN algorithm in table model and extracting Volterra series by usingX-parameters provide new approaches for device model and broaden the mind of modelwhich may improve the development of device model.更多还原