一种波导耦合的AlGaN / GaN HEMT 太赫兹探测器

A Waveguide-coupled AlGaN / GaN HEMT Terahertz Detector

中文关键词:  太赫兹  波导  微带线  阻抗匹配  HEMT

英文关键词:terahertz  waveguide  microstrip line  impedance matching  HEMT

中文摘要:

      自由空间的太赫兹电磁波与太赫兹天线/ 探针之间的耦合通常是通过波导或硅透镜来实现的。基于波导的耦合方案可以提供比透镜耦合方案更高的耦合效率,而此前AlGaN/ GaN HEMT 太赫兹探测器/ 混频器具有高阻抗的特性,因此一般采用硅透镜耦合。文中仿真设计了一种110 GHz 的波导耦合型AlGaN/ GaN HEMT 太赫兹直接探测器,采用波导-微带过渡结构和微带线阻抗匹配结构使探测器的阻抗降低至275 Ω,在降低热噪声电压的同时具有高的响应度。在设计好探测器各部分结构后,对其进行整体全波仿真、数据提取与后处理计算,最后可得到探测器的性能指标即噪声等 效功率(NEP)。结果表明:在110 GHz 的频率下,太赫兹探测器的NEP 可达到22 pW/ Hz,与透镜耦合型直接探测器灵敏度相当,其中该探测器中HEMT 混频器的栅长和栅宽分别为1 μm 和150 μm。仿真结果还表明通过将栅长从1 μm缩减至100 nm,可以进一步降低探测器的NEP,提高探测器的灵敏度。

英文摘要:

      The coupling between terahertz electromagnetic waves in free space and terahertz antennas/ probes is usually achieved through waveguides or silicon lenses. Waveguide-based coupling schemes can provide higher coupling efficiency than lens coupling schemes, whereas previously AlGaN/ GaN HEMT terahertz detectors/ mixers had the characteristic of high impedance and therefore generally used Si-lens coupling. In this paper, a waveguide-coupled AlGaN/ GaN HEMT terahertz direct detector is simulated and designed for 110 GHz applications. A waveguide-microstrip transition structure and the microstrip line impedance matching structure are applied to reduce the detector impedance to 275 Ω, which provides high responsivity while reducing the thermal noise voltage. After designing the structure of each part of the detector, the overall full-wave simulation, data extraction and postprocessing are performed, and finally the figure of merit of the detector, i. e. , the noise-equivalent power ( NEP), can be obtained. The results show that the NEP of the terahertz detector is about 22 pW/ Hz at 110 GHz, which is comparable to the sensitivity of the Si-lens coupled terahertz direct detector, where the gate length and gate width of the HEMT mixer in this detector are 1 μm and 150 μm, respectively. The simulation results suggest the NEP could be further reduced and the detector sensitivity can be improved by shrinking the gate length from 1 μm to 100 nm.