HEMT太赫兹探测器响应度和NEP的检测与分析

在0.8～1.1 THz内,对AlGaN/GaN高电子迁移率晶体管(HEMT)太赫兹探测器的响应度和噪声等效功率进行了具体测试和分析。在太赫兹波辐射下,HEMT太赫兹探测器源漏端产生能被栅压灵敏调控的直流光电流。该型探测器在300 K和77 K下的电流响应度分别为83 mA/W和4.1 A/W,电压响应度分别为4 kV/W和50 kV/W,噪声等效功率分别达到22 pW/Hz0.5和1 pW/Hz0.5。采用两种较为典型的测量方法,通过对实验结果的比较,确定了影响该类型探测器的响应度和噪声等效功率的主要因素,并提出了增强响应度和降低噪声等效功率的具体措施。     

蝶形天线增强的HEMT室温太赫兹探测器

介绍了一种基于GaN/AlGaN高电子迁移率晶体管(HEMT)的高速、高灵敏度室温太赫兹探测器。在太赫兹波辐射下,HEMT源漏端产生直流光电流,并能被栅压灵敏地调控。探测器中新颖的蝶形天线设计使接收到的太赫兹电场得到显著增强,提高了探测器的响应度。通过测量探测器对不同偏振方向的太赫兹光的响应,有效验证了蝶形天线对太赫兹电场的增强作用。室温下,探测器的等效噪声功率约为5×10-10W/Hz21,平均响应度达42mA/W。实验结果表明,光电流的产生与二维电子气沟道的场效应特性和入射太赫兹波电场在电子沟道中的分布密切相关。自混频理论能很好地描述实验结果。     

High Current Responsivity and Wide Modulation Bandwidth Terahertz Detector Using High-Electron-Mobility Transistor for Wireless Communication

A high-current-responsivity terahertz (THz) detector was fabricated using a broadband bow-tie antenna and an InAlAs/InGaAs high-electron-mobility transistor (HEMT) with a short gate length. High-current responsivity can be achieved by using a short gate length; the resulting high transconductance exhibited ballistic transport in the channel. We fabricated the HEMT detector with a 50-nm-long channel; the transconductance was 1.2 S/mm and the subthreshold slope was 120 mV/dec, yielding a high-current responsivity (～5 A/W) and a cutoff frequency of 460 GHz. We also measured the modulation bandwidth of the THz detector using a heterodyne mixing technique with a uni-traveling carrier photodiode (UTC-PD) for providing the radio frequency (RF) and a frequency multiplier as a local oscillator. The intensity of the intermediate signal (IF) was measured by changing the frequency of the UTC-PD; very high bandwidths of up to 26 GHz were obtained. The experimental results agree well with electromagnetic simulations, which indicate that the bandwidth is determined by the external circuit. The conversion gain from RF to IF was ?2 dB in the heterodyne mixing by using the HEMT detector.     

Pt/CdS Schottky势垒紫外探测器的研制

介绍了Pt/CdS金属半导体接触Schottky势垒形成及In/CdS的欧姆接触工艺研究,由此制成了紫外探测器.测试了探测器的Ⅰ-Ⅴ特性,零偏下的光谱响应和器件的频率响应.观察了器件的反偏响应情况.获得的探测器在λ=440am处加两伏反偏时的响应率为0.17A/W,内量子效率最大可达64%.     

基于65 nm标准CMOS工艺的3.0 THz 探测器

基于Dyakonov和Shur等离子体波振荡原理设计并流片制备了一种采用65 nm标准CMOS工艺的3.0THz探测器,探测器包括贴片天线、NMOS场效应晶体管、匹配网络及陷波滤波器。探测器在室温条件下可达到526 V/W的响应率(Rv)和73 pW/Hz1/2的噪声等效功率(NEP)。采用该探测器和步进电机搭建了太赫兹扫描成像系统,获得了太赫兹源出射光斑的远场形状,光斑的半高宽(FWHM)为240μm;并对聚甲醛牙签和树叶进行了扫描成像实验,结果表明CMOS太赫兹探测器在成像领域有潜在的应用前景。     

双顶栅极石墨烯的太赫兹信号源

为探索产生太赫兹信号的新型材料与器件,提出一种基于石墨烯的具有双顶栅极结构的场效应管器件(FET)模型,并对此器件所具有的太赫兹特性进行研究。使用费米函数推导计算发现,器件在一定的太赫兹频段存在负电导的可能,同时得到了石墨烯综合电导与偏置电压、弛豫时间、栅极电压以及温度等因素之间的关系,表明此器件具有作为新型太赫兹源的潜力。     

基于铟镓砷材料的新型太赫兹/亚毫米波探测器研究

对一种基于生长在半绝缘InP衬底上InGaAs外延材料的新型太赫兹室温探测器进行研究。首先在HFSS理论计算的基础上对器件天线阻抗、驻波比、辐射方向图等特性参数进行分析。其次,通过光刻、腐蚀、溅射、点焊等工艺制作出对称金属电极天线耦合的太赫兹探测器件。结合自己搭建的0.037 5 THz器件响应测试系统,得到铟镓砷太赫兹探测器件在不同偏置电流和不同调制频率下的器件响应曲线。结果表明器件具有明显的光电信号和快的响应速度。通过利用高莱探测器进行标定,得到器件在0.037 5 THz时的电压灵敏度优于6 V/W,器件噪声等效功率NEP优于1.610-9 W/Hz1/2,器件响应时间优于300 s。     

基于场效应晶体管的太赫兹探测器中天线设计的一种有效方法

在场效应晶体管太赫兹探测器中,合理的天线设计可以增强晶体管和太赫兹波之间的耦合效率,从而提高太赫兹探测器的响应度.提出一种基于晶体管栅极边缘沟道电场的仿真来设计平面天线的方法.这种方法尤其适用于太赫兹波段晶体管输入阻抗不容易得到的情况.通过流片完成的基于氮化镓高电子迁移率晶体管的太赫兹探测器的响应度测试证实了这种方法的有效性.集成碟形天线和双偶极子天线的太赫兹探测器最大响应度分别在170.7 GHz(1568.4 V/W)和124.3 GHz(1047.2 V/W)频点处测得,这个测试结果接近基于晶体管栅极边缘沟道电场的仿真结果.     

基于超材料的太赫兹幅度调制器设计

提出了一款基于超材料的太赫兹幅度调制器,其结构由开口"弓"形超材料结构、高电子迁移率晶体管、斜十字馈线和碳化硅衬底四部分构成."弓"形超材料结构开口处的连通和断开两种状态将对通过该结构的太赫兹波产生不同的响应.在开口处添加高电子迁移率晶体管可模拟开口连通和断开的效果.当对晶体管上的栅极不施加偏压时,超材料结构开口相当于导通,对太赫兹波透射系数高;当对晶体管上的栅极施加偏压时,超材料结构开口相当于断开,对太赫兹波透射系数低.仿真结果表明,在0.22 THz处,对晶体管栅极不施加偏压时,调制器的透射系数为0.579;对晶体管栅极施加偏压时,调制器的透射系数为0.040.通过公式计算得到其调制深度为93％,而且对x和y极化入射波具有不敏感的特性.同时,通过分析0.22 THz处的电场分布和表面电流分布研究了该太赫兹调制器的工作原理.所设计的太赫兹调制器具有调制深度高、结构简单和易于加工等特点,在太赫兹通信领域具有广阔的应用前景.     

新型SiO2栅介质非晶硅薄膜晶体管室温红外探测器

对用作室温红外探测敏感单元的非晶硅薄膜晶体管进行了研究,提出了一种新型SiO2栅介质非晶硅薄膜晶体管室温红外探测器。该探测器的基本工作机理与传统的SiN2栅介质薄膜晶体管相类似,但在器件性能方面不仅具有较高的响应度,而且具有更好的温度稳定性;在制作工艺方面具有更高的工艺重复性和栅介质淀积的均匀性。     

新型SiO2栅介质非晶硅薄膜晶体管室温红外探测器

对用作室温红外探测敏感单元的非晶硅薄膜晶体管进行了研究，提出了一种新型SiO2栅介质非晶硅薄膜晶体管室温红外探测器。该探测器的基本工作机理与传统的SiNx栅介质薄膜晶体管相类似，但在器件性能方面不仅具有较高的响应度，而且具有更好的温度稳定性；在制作工艺方面具有更高的工艺重复性和栅介质淀积的均匀性。     

液氮制冷的AlGaN/GaN HEMT太赫兹探测器阵列特性研究

为充分发挥AlGaN/GaN高电子迁移率晶体管 (High-Electron-Mobility Transistor, HEMT)太赫兹探测器阵列的高电子迁移率优势,文中研究了HEMT太赫兹探测器阵列在77 K下的探测特性。使用液氮杜瓦为降温主体搭建了适用于焦平面 (Focal-Plane Array, FPA)芯片的低温系统,实现了对焦平面芯片常温与低温下的对比测试。温度从300 K降到77 K时,探测器阵列像元的平均响应度提高近3倍,平均噪声有小幅增大,340 GHz时平均噪声等效功率 (Noise Equivalent Power, NEP)从45.1 pW/Hz1/2降低到了19.4 pW/Hz1/2,灵敏度提高两倍以上。与硅透镜耦合的单元探测器相比,阵列像元的灵敏度提升仍有较大空间。主要是由于各像素点最佳工作电压的不一致,导致在给定统一工作电压下像元间的响应度和噪声都表现出较大的离散性,文中讨论了降低最佳工作电压离散度的可能解决方案。     

Enhanced Plasma Wave Detection of Terahertz Radiation Using Multiple High Electron-Mobility Transistors Connected in Series

We report on enhanced room-temperature detection of terahertz radiation by several connected field-effect transistors. For this enhanced nonresonant detection, we have designed, fabricated, and tested plasmonic structures consisting of multiple InGaAs/GaAs pseudomorphic high electron-mobility transistors connected in series. Results show a 1.63-THz response that is directly proportional to the number of detecting transistors biased by a direct drain current at the same gate-to-source bias voltages. The responsivity in the saturation regime was found to be 170 V/W with the noise equivalent power in the range of ${hbox{10}}^{-7}~{hbox{W/Hz}}^{0.5}$ . The experimental data are in agreement with the detection mechanism based on the rectification of overdamped plasma waves excited by terahertz radiation in the transistor channel.      

Parametric instability in the resonance detector of terahertz radiation based on FET with cylindrical gate electrode

A possibility of the parametric instability in the resonance detector of the modulated terahertz radiation is analyzed. The detector represents a system of capacitively coupled plasma and mechanical resonators. A layer of 2D electron gas with a relatively high electron mobility and a cylindrical gate electrode that is fixed at the ends serve as the first and second resonators, respectively. The method of coupled oscillations is used to obtain the dependence of the minimum threshold pump power of the plasma circuit that corresponds to the excitation of the parametric instability on the main geometrical and electric parameters of the system.     

Parametric instability in a nanoelectromechanical detector of modulated terahertz radiation on the basis of a high electron mobility transistor with a mobile elastic gate

Parametric instability in a modulated terahertz radiation detector based on a high electron mobility transistor with a mobile elastic gate fabricated from a conductor in the form of a micronanocantilever is studied in detail. The analysis is based on the method of coupled oscillations and subsequent testing by direct numerical integration of the original equations. The thresholds and increments of the instability are determined. The feasibility of practical realization of conditions for parametric instability in such detectors is discussed.     

基于AlGaN/GaN场效应晶体管的太赫兹焦平面成像传感器

太赫兹波成像技术在人体安检、医学成像、无损检测等领域具有广泛的应用前景。文中面向高速、高灵敏度和便携式太赫兹成像应用需求,设计实现了一种基于AlGaN/GaN高电子迁移率晶体管自混频检测机制的太赫兹焦平面成像传感器。该焦平面成像传感器由探测器阵列芯片和CMOS读出电路通过倒装互连实现,阵列规模达到3232。探测器阵列中具有对管差分功能的像元设计通过提高探测器的电压响应度和抑制共模电压噪声,提高了焦平面成像的灵敏度。焦平面成像传感器的输出模拟信号通过片外的模数转换（ADC）芯片转化为数字信号,由现场可编程门阵列（FPGA）采集后通过Camera Link图像数据与通信接口发送到计算机。利用该焦平面成像传感器,演示实现了太赫兹光斑、太赫兹干涉环和太赫兹光照下的旋转塑料叶片的视频成像,帧频达到30 Hz。     

Low frequency characteristics of a quasioptical Schottky diode detector part II: Experimental results

A detailed experimental study of the low frequency (video) response of a quasioptical Schottky diode detector over the microwave and FIR wavelength range is presented. An optimization of the responsivity versus the bias current is proposed and a generalized curve of the saturation power versus the FIR wavelength is given. This curve defines for any antenna point-contact Schottky diode detector, suitable for FIR detection, the power range for a linear detector response. A simple method is also described to calculate the coupling efficiency of the laser radiation into the antenna reception pattern.     

High-Temperature Tunneling Quantum-Dot Intersublevel Detectors for Mid-Infrared to Terahertz Frequencies

Quantum-dot infrared photodetectors have emerged as attractive devices for sensing long wavelength radiation. Their principle of operation is based on absorption of radiation via intersublevel transitions in quantum dots. Multiple layers of self-organized ln(Ga)As/Ga(Al)As quantum dots are generally incorporated in the active region of these devices. Three-dimensional quantum confinement allows normal incidence operation. This paper describes a novel variation in the design of these devices which allows a significant reduction of the dark current, high temperature operation and extension of operation to terahertz frequencies. The principle of operation and operating characteristics of this device - the tunnel quantum-dot intersublevel detector - are described. Operation is demonstrated from 6-80 mum at temperatures up to 300 K with acceptable values of peak responsivity (0.1-0.75 A/W) and specific detectivity (10⁷-10¹¹cm ldr Hz^1/2/W^-1 , depending on temperature and wavelength).     

Ultrafast Photo-Thermal Switching of Terahertz Spin Currents

Dissipationless and scattering-free spin-based terahertz electronics is the futuristic technology for energy-efficient information processing. Femtosecond light pulse provides an ideal pathway for exciting the ferromagnet (FM) out-of-equilibrium, causing ultrafast demagnetization and superdiffusive spin transport at sub-picosecond timescale, giving rise to transient terahertz radiation. Concomitantly, light pulses also deposit thermal energy at short timescales, suggesting the possibility of abrupt change in magnetic anisotropy of the FM that could cause ultrafast photo-thermal switching (PTS) of terahertz spin currents. Here, a single light pulse induced PTS of the terahertz spin current manifested through the phase reversal of the emitted terahertz photons is demonstrated. The switching of the transient spin current is due to the reversal of the magnetization state across the energy barrier of the FM layer. This demonstration opens a new paradigm for on-chip spintronic devices enabling ultralow-power hybrid electronics and photonics fueled by the interplay of charge, spin, thermal, and optical signals.     

采用CMOS太赫兹波探测器的成像系统

太赫兹波成像技术在生物医疗和安全检测等领域具有广阔的应用前景。针对新一代信息技术对便携式太赫兹波成像设备的需求，设计了基于CMOS太赫兹波探测器的成像系统。该系统包括一款CMOS太赫兹波探测器、片外模数转换器（ADC）、FPGA数字信号处理器、二位步进机、四个抛物面镜和太赫兹波辐射源等。CMOS太赫兹波探测器集成了片上贴片天线以及作为检波元件的NMOS晶体管，探测器由180 nm标准CMOS工艺制成。太赫兹波探测器的输出被片外模数转换器（ADC）采集并转换为数字信号，该数字信号被FPGA采集并传输到电脑上成像。所有上述元件均被装备在印刷线路板（PCB）上以减小系统体积。该系统实现了透射式太赫兹波扫描成像而无需斩波-锁相技术，并给出在860 GHz的太赫兹波照射下隐藏在信封内部金属的成像结果。