Low Noise Hot-Electron Bolometer Mixers for Terahertz Frequencies

Hot-electron bolometer (HEB) mixers are used in many low noise heterodyne radio astronomical receivers. Their noise temperature is at the level of 10–15 times the quantum limit. However, their gain bandwidth is a serious limiting factor. Here we review the state of the art of the HEB mixers gain bandwidth for different materials and substrates. We compare the gain bandwidth of HEB mixers made on bulk substrates and thin membranes. Finally, results for MgB₂ thin films for broadband HEB mixers are discussed.      

太赫兹技术在水泥基材料研究中的应用

本文介绍了太赫兹波的特性以及太赫兹技术的工作原理及其应用,重点介绍了太赫兹时域光谱技术和太赫兹成像技术在水泥水化过程、水泥基材料的微观结构检测和水泥基材料耐久性能三方面的研究进展.利用太赫兹光谱技术可跟踪硅酸三钙、硅酸二钙以及主要水化产物水化硅酸钙、氢氧化钙在水化过程中的变化情况;利用水分对太赫兹波强烈吸收的特性,能够...     

毫米波扩展互作用器件

扩展互作用器件是一种采用慢波谐振系统作为高频互作用电路的真空电子器件,是目前能够在毫米波亚毫米波段提供大功率输出的重要器件之一。本文给出了目前国内外毫米波亚毫米波段扩展互作用器件（EIK和EIO）技术的发展情况,并介绍了扩展互作用器件在毫米波亚毫米波段的技术特点和最新研究趋势。     

不断发展中的行波管技术

自从上世纪40年代第一支行波管改进以来,行波管技术不断发展,成为真空器件最重要的一个分支,并在各类军事与民用系统中发挥了重要的作用。目前行波管正朝着微/小型化、大功率和高频率三个方向发展。近年来,随着化学物半导体技术的发展,行波管受到固态器件的挑战,但是由于行波管所具有的宽频带、高功率、高效率及高频率工作的优点,在竞争中仍然具有生命力,还是军事和类似商业应用的主要产品。     

太赫兹近场光学亚表面检测技术研究

研究了太赫兹散射式扫描近场光学显微镜（Terahertz scattering-type scanning near-field optical microscopy,THz s-SNOM）对亚表面金属微纳结构的显微成像检测。首次采用自主搭建的THz s-SNOM系统对表面覆盖了六方氮化硼薄膜的金微米线进行太赫兹近场显微测量,获得了具有纳米量级空间分辨率和较高对比度的近场显微图。结合全波数值模拟,分析了THz s-SNOM探测亚表面金属微纳结构的空间分辨率、近场散射信号强度和成像对比度。研究表明,THz s-SNOM具有优良的亚表面显微成像检测能力,可应用于微纳电子器件的亚表面结构表征和缺陷检测。     

Material and process considerations for terahertz planar nanodevices

Using a two-dimensional ensemble Monte Carlo method, we have studied the capacitances in a planar nano-diode, called the self-switching device (SSD) that is based on an asymmetric nanochannel. We show that the terahertz (THz) response of the SSD can be affected by the dielectric constant and width of the insulating trenches that confine the nanochannel of the diode. The simulations reveal that the capacitive coupling over the insulating trenches has little influence on the device RF properties below 100 GHz, but significantly affects the device performance around and beyond 1 THz. We show that the capacitance is more sensitive to the dielectric constant of the substrate but is relatively less sensitive to the width of the insulating trench or the dielectric constant of the infill material in the insulating trenches. This differs significantly from a conventional capacitor with two parallel plates. The findings in this work provide useful implications in optimizing the material and lithography parameters of such and similar nanodevices for THz applications.     

THz Spectroscopy of Liquid Crystals from the CB Family

Liquid crystals represent a very interesting material system but their properties in the THz range have not been extensively investigated yet. In this paper we investigate the THz properties of four liquid crystals from the CB family (5CB, 6CB, 7CB and 8CB). In addition to absolute refractive indices and absorption coefficients we present accurate birefringence measurements for different electric fields and temperatures.     

Free-charge carrier profile of iso- and aniso-type Si homojunctions determined by terahertz and mid-infrared ellipsometry

We present an optical, non-destructive, non-contact method of determining the silicon homojunction epilayer free-charge carrier concentration profile and thickness by means of combined terahertz (0.2-1 THz) and mid-infrared (10-50 THz) spectroscopic ellipsometry investigation. A dual homojunction iso- and aniso-type silicon sample is investigated. Application of analytical models for iso-type and aniso-type homojunctions results in an excellent match between calculated and experimental data. Best-match model calculated parameters are found to be consistent with electrical spreading resistance epilayer thickness and resistivity values.     

Terahertz Schottky barrier diodes with various isolation designs for advanced radio frequency applications

High performance nanometer NiSi2-Si Schottky barrier diode arrays (SBDA) with various isolation designs, including poly Si gate (PSG) and resist protection oxide (RPO), are developed for advanced radio frequency applications. Radio frequency performances of these developed SBDAs are investigated and compared to that with the conventional shallow trench isolation. All of the SBDAs are fabricated with a foundry state-of-the -art 45 nm complementary metal oxide semiconductor technology. Both of PSG and RPO insulated SBDAs have higher cutoff frequency and a simpler preparation process. Specifically, the PSG insulted SBDA could achieve a cutoff frequency of up to 4.6 THz.