Advanced Tunneling-Based Detectors and Imaging Systems for Millimeter-Wave and THz Sensing and Imaging

该项目将研究和开发性能优越、功能先进的毫米波和太赫兹探测和成像系统设备。这一技术领域具有广泛的社会效益，包括辐射测量和遥感(气候学、射电天文学、化学光谱学)等科学应用，穿透屏障成像等安全应用(即通过包装、墙壁等探测人或物体的能力)。和爆炸物探测，以及其他传感应用，例如通过雾、沙和其他可见遮蔽物的航空电子制导和成像、医学成像和工业过程控制(例如，检测地下缺陷)。这项研究涉及两个主要领域：(1)超灵敏、低噪声异质结构带间隧道探测器的设备级演示；(2)原型天线耦合探测器和成像阵列的系统级演示。正在探索的设备承诺的噪音水平比传统方法低30多倍。这种低得多的噪声使系统得到极大简化，从而大大降低了尺寸、重量和成本，并使毫米波和太赫兹成像在成本敏感型商业和民用应用中得以实际实施和开发。该项目还将生产提供光谱和偏振灵敏度的成像阵列原型，允许的不仅仅是“灰度”成像。这种增强的功能对于材料识别和表征以及在成像应用中提供区分类似物质和对象的能力是有价值的。该项目通过研究生水平的研究机会，为高中科学和技术外展的学生提供重要的教育机会。该项目采用跨学科方法，在设备设计和优化以及成像阵列和系统设计方面都做出了努力。这种方法确保所开发的设备满足系统体系结构的需求，并且系统体系结构可以被定制以充分挖掘设备的潜力。将探索两种新兴的器件技术：异质结后向二极管(HBD)和隧穿场效应管(TFET)；使用带间隧道来产生探测器？二阶非线性在灵敏度和噪声性能方面具有显著优势；灵敏度可以超过肖特基和场效应晶体管(FET)探测器的热离子发射施加的基本限制，同时工作在零偏压下，具有低闪烁(1/f)噪声和高灵敏度。这些设备将与新型配置的平面天线单片集成，以实现毫米波和太赫兹波段的频率调谐和极化分辨检测。仿真结果表明，实现0.05PW/Hz1/2及以下的噪声等效功率是可能的。通过改进器件设计(即对外延晶片结构的改进，重点放在新颖的阶梯形势垒设计上)和缩放(通过先进的制造工艺减少关键的横向尺寸)，将展示工作频率达到太赫兹的器件。具有频率调谐能力(通过平面环形缝隙天线的可变有源调谐实现)和极化辨别(也使用加载的环形缝隙天线)的成像阵列将被原型和评估，以验证用于成像应用的探测器的性能。研究范围包括探索带间隧道二极管和隧穿场效应管(TFET)的相关物理，详细的器件设计和优化，器件的实验制造和表征以及器件物理模型的验证，以及利用这些器件的成像阵列的原型。智能影响包括促进对利用波段间隧道进行毫米波和太赫兹探测的设备设计的理解，以及成像阵列体系结构和在此频率范围内进行光谱和偏振分辨成像的方法。这些设备和成像阵列有望在科学、工业和安全领域的各种检测和成像应用中找到应用。

This project will investigate and develop devices for millimeter-wave and THz detection and imaging systems with superior performance and advanced functionalities. This technological area has a wide range of applications of societal benefit, including scientific applications such as radiometry and remote sensing (climatology, radio astronomy, chemical spectroscopy), security applications such as through-barrier imaging (i.e. the ability to detect persons or objects through packaging, walls, etc.) and explosive detection, and other sensing applications such as avionic guidance and imaging through fog, sand, and other visible obscurants, medical imaging, and industrial process control (e.g., detection of subsurface defects). The research involves two main thrust areas: (1) device-level demonstration of ultra-sensitive, low-noise heterostructure interband tunneling-based detectors, and (2) system-level demonstration of prototype antenna-coupled detectors and imaging arrays. The devices being explored promise noise levels more than 30 times lower than conventional approaches. This much lower noise allows systems to be greatly simplified, leading to much lower size, weight, and cost, and enabling practical implementation and exploitation of millimeter-wave and THz imaging in cost-sensitive commercial and civilian applications. The project will also produce prototype imaging arrays offering spectroscopic and polarization sensitivity, allowing more than just "grayscale" imaging. This enhanced functionality is valuable for material identification and characterization, as well as to provide the ability to discriminate among similar substances and objects in imaging applications. The project provides significant educational opportunities for students from high school science and technology outreach through graduate-level research opportunities. The project features an interdisciplinary approach, with effort in both device design and optimization as well as imaging array and system design. This approach ensures that the devices developed serve the needs of the system architectures, and the system architectures can be tailored to fully tap the potential of devices. Two emerging device technologies will be explored: heterostructure backward diodes (HBDs) and tunneling field-effect transistors (TFETs); using interband tunneling to generate the detectors? second-order nonlinearity provides significant advantages in terms of sensitivity and noise performance; the sensitivity can exceed the fundamental limits imposed by thermionic emission in Schottky and field-effect transistor (FET) detectors, while operating with zero applied bias for low flicker (1/f) noise and high sensitivity. These devices will be monolithically integrated with planar antennas in novel configurations to enable frequency tuning and polarization-resolved detection in the millimeter-wave and THz regimes. Simulations indicate that noise equivalent power (NEP) of 0.05 pW/Hz1/2 and below should be possible to achieve. Through device design improvements (i.e., modifications to the epitaxial wafer structure, focusing on novel stepped-barrier designs) and scaling (reduction in critical lateral dimensions through advanced fabrication processing), devices with operational frequencies well into the THz will be demonstrated. Imaging arrays with frequency tuning capability (implemented with varactive tuning of planar annular slot antennas) and polarization discrimination (also using loaded annular slot antennas) will be prototyped and assessed to validate the performance of the detectors for imaging applications. The research scope includes exploration of the relevant physics in interband tunnel diodes and tunneling field effect transistors (TFETs), detailed device design and optimization, experimental fabrication and characterization of devices and validation of the device physical models, and prototyping of imaging arrays leveraging these devices. The intellectual impact includes advancing the understanding of device designs for leveraging interband tunneling for millimeter-wave and THz detection, as well as imaging array architectures and approaches to spectroscopic and polarization-resolved imaging in this frequency regime. These devices and imaging arrays can be expected to find applications in a diverse range of detection and imaging applications in the scientific, industrial, and security arenas.