高漏偏压下AlGaN/GaN HEMT噪声性能的研究

The advent of fully integrated GaN PA-LNA circuits makes it meaningful to investigate the noise performance under high drain bias. However, noise performance of AlGaN/GaN HEMTs under high bias has not received worldwide attention in theoretical studies due to its complicated mechanisms. The noise value is moderately higher and its rate of increase is fast with increasing high voltage. In this paper, several possible mechanisms are proposed to be responsible for it. Impact ionization under high electric field incurs great fluctuation of carrier density, which increases the drain diffusion noise. Besides, higher gate leakage current related shot noise and a more severe self-heating effect are also contributors to the noise increase at high bias. Analysis from macroscopic and microscopic perspectives can help us to design new device structures to improve noise performance of AlGaN/GaN HEMTs under high bias.     

AlGaN/GaN HEMT 小信号模型提取方法的改进

The accurate extraction of AlGaN/GaN HEMT small-signal models, which is an important step in largesignal modeling, can exactly reflect the microwave performance of the physical structure of the device. A new method of extracting the parasitic elements is presented, and an open dummy structure is introduced to obtain the parasitic capacitances. With a Schottky resistor in the gate, a new method is developed to extract Rg. In order to characterize the changes of the depletion region under various drain voltages, the drain delay factor is involved in the output conductance of the device. Compared to the traditional method, the fitting of S 11 and S 22 is improved, and fT and fmax can be better predicted. The validity of the proposed method is verified with excellent correlation between the measured and simulated S-parameters in the range of 0.1 to 26.1 GHz.     

A Ku band internally matched high power GaN HEMT amplifier with over 30%of PAE

正We report a high power Ku band internally matched power amplifier(IMPA) with high power added efficiency(PAE) using 0.3μm AlGaN/GaN high electron mobility transistors(HEMTs) on 6H-SiC substrate.The internal matching circuit is designed to achieve high power output for the developed devices with a gate width of 4 mm.To improve the bandwidth of the amplifier,a T type pre-matching network is used at the input and output circuits,respectively.After optimization by a three-dimensional electromagnetic(3D-EM) simulator,the amplifier demonstrates a maximum output power of 42.5 dBm(17.8 W),PAE of 30%to 36.4%and linear gain of 7 to 9.3 dB over 13.8-14.3 GHz under a 10%duty cycle pulse condition when operated at V_(ds) = 30 V and V_(gs)=—4 V.At such a power level and PAE,the amplifier exhibits a power density of 4.45 W/mm.     

基于HBT工艺的低三阶交调失真射频放大器优化设计

针对宽带大信号容量无线系统对低三阶交调失真射频放大器的迫切需求,从放大器偏置点优化和片上散热优化两个方面研究了基于HBT工艺的低三阶交调失真射频放大器优化设计方法。分析了达林顿复合结构射频放大器交调特性与直流偏置点的关系,给出了放大器最佳三阶交调直流偏置点。提出了一种优化散热的输出级分散布局电路结构,减小了片上温升带来的三阶交调性能恶化。应用提出的优化设计理论方法,基于2μm AlGaAs/GaAs HBT工艺,设计了一款工作于0.05～1 GHz的低三阶交调失真射频放大器。测试结果表明,该放大器实现了42.1 dBm的输出三阶交调点,三阶交调与1 dB压缩点之比达到了21.2 dB。     

应用于AlGaN/GaN HEMTs MMIC薄膜电阻的特性与可靠性

TaN和NiCr是AlGaN/GaN HEMTs微波集成电路中薄膜电阻最为常用的两种材料.文中对比了在SiC衬底上生长的这两种材料的薄膜电阻的可靠性.通过TaN和NiCr薄膜电阻的对比,发现TaN薄膜电阻的方块电阻(Rs)随着退火温度的上升而增大,然而NiCr薄膜电阻的Rs却出现相反的趋势.同时发现随着退火温度的上升TaN薄膜电阻的s.和接触电阻(Rc)的变化远远小于NiCr薄膜电阻的变化.在400℃退火及等离子刻蚀机的氧等离子暴露后,TaN薄膜电阻的Rs只下降了0.7Ω,大概2.56%,并且Rc上升了0.1Ω,大概6.6%.但是NiCr薄膜电阻的Rs.和Rc在不同的退火条件下经过氧等离子暴露后发生了很大的变化.因此,TaN薄膜电阻在氮气保护下经过400℃退火后在氧等离子暴露下更为稳定.     

Annealing before gate metal deposition related noise performance in AIGaN/GaN HEMTs

For a further improvement of the noise performance in A1GaN/GaN HEMTs, reducing the relatively high gate leakage current is a key issue. In this paper, an experiment was carried out to demonstrate that one method during the device fabrication process can lower the noise. Two samples were treated differently after gate recess etching： one sample was annealed before metal deposition and the other sample was left as it is. From a comparison of their Ig-Vg characteristics, a conclusion could be drawn that the annealing can effectively reduce the gate leakage current. The etching plasma-induced damage removal or reduction after annealing is considered to be the main factor responsible for it. Evidence is given to prove that annealing can increase the Schottky barrier height. A noise model was used to verify that the annealing of the gate recess before the metal deposition is really effective to improve the noise performance of AIGaN/GaN HEMTs.     

蒸栅前退火与AlGaN/GaN HEMT噪声性能关系的研究

为进一步提高AlGaN/GaN HEMT的噪声性能,如何才能降低其相对较高的栅漏电是较为棘手的问题之一。作者通过实验证明了可降低其噪声的器件制作过程中的一项工艺步骤。两个AlGaN/GaN样片在刻蚀栅槽后被分别不同处理,一个蒸发栅金属前退火,另一个直接蒸发栅金属。比较二者的Ig－Vgd直流特性曲线,可发现蒸栅前进行退火处理可大大降低栅漏电。数据分析表明：退火可提高肖特基势垒;刻蚀过程中的等离子体可引发损伤,退火导致的损伤消除是栅漏电减小的主要原因。作者引用了一个噪声模型来证明蒸栅前退火确实可以有效地提高AlGaN/GaN HEMT的噪声性能。     

AlGaN/GaN HEMT多偏置下CV特性的研究

电容电压特性是分析半导体器件性能的一个有效手段,而且是GaN HEMT器件大信号模型建模的重要步骤之一。本文提出一种多偏置电容电压的测试方法,并讨论了Cgs和Cgd的物理意义及其随偏置电压Vgs和Vds的变化规律。提出一种能够反映Cgs和Cgd特性的电容模型,与测试电容数据有很好的拟合效果,并且用器件的功率特性验证了该电容模型在非线性仿真的准确性。     

35弹头机械引信自炸机构的分析计算

对35弹头机械引信的自炸机构进行了理；论分析计算，通过建立计算自炸机构自炸转速的数学模型，分析了影响自炸机构的各种因素，从而确定生产过程中的质量控制重点，采取相应的措施，以确保35弹头机械引信产品质量。     

应用于AlGaN/GaN HEMTs MMIC薄膜电阻的特性与可靠性

TaN和NiCr是AlGaN/GaN HEMTs微波集成电路中薄膜电阻最为常用的两种材料.文中对比了在SiC衬底上生长的这两种材料的薄膜电阻的可靠性.通过TaN和NiCr薄膜电阻的对比,发现TaN薄膜电阻的方块电阻(Rs)随着退火温度的上升而增大,然而NiCr薄膜电阻的Rs却出现相反的趋势.同时发现随着退火温度的上升TaN薄膜电阻的s.和接触电阻(Rc)的变化远远小于NiCr薄膜电阻的变化.在400℃退火及等离子刻蚀机的氧等离子暴露后,TaN薄膜电阻的Rs只下降了0.7Ω,大概2.56%,并且Rc上升了0.1Ω,大概6.6%.但是NiCr薄膜电阻的Rs.和Rc在不同的退火条件下经过氧等离子暴露后发生了很大的变化.因此,TaN薄膜电阻在氮气保护下经过400℃退火后在氧等离子暴露下更为稳定.