Integrated Terahertz Measurement Systems based on Heterogeneously Integrated Sensors

长期以来，电磁频谱的太赫兹(或亚毫米波)区域一直被认为对射电天文学、大气物理和遥感等领域的基础科学研究和进步至关重要。此外，新的和新兴的设备概念有望为进一步的科学研究以及在成像、无损测试和评估以及高带宽通信中的重要应用打开这一基本上无法进入的频谱。不幸的是，开发这些新技术所需的基础设施和测量工具仍然严重有限。目前实现亚毫米波长测量仪器的方法主要基于使用波导接口的模块化方法。这导致了完全组装的测量仪器具有相当大的几何面积，可能被证明是笨重的或不适合许多重要场景，例如，当要测试的设备或系统必须保持在诸如真空室或低温恒温器之类的屏蔽罩内的情况下。该项目致力于解决这一关键问题，开发基于高性能太赫兹传感器的紧凑型和低轮廓测量仪器，这些传感器与微机械加工的支撑膜异质集成，允许在太赫兹频率下直接接触原位表征平面设备和系统。因此，这项工作将通过提供新的和先进的计量仪器，允许进行目前不可能或不可行的测量，对不断增长的太赫兹研究界产生广泛的影响。创造新的测量技术和能力是科学进步的基础；科学发现和工程学的进步是建立在为实验和研究开辟新的物理领域的仪器的基础上的。这项工作代表着朝着开发仪器迈出的第一步、关键的一步和必要的一步，该仪器克服了限制当前太赫兹计量方法的固有缺陷。该项目的目标和范围是通过开发基于异质集成的仪器技术来推进太赫兹设备、组件和系统的测量和表征的基础设施。这项研究的重点是跨材料系统(例如，III-V半导体和硅)和跨物理领域(例如，电子和机械)的异质集成。为此，将采取的具体方法包括三个主要方面：(1)开发异质集成到薄硅膜上的低寄生太赫兹肖特基二极管传感器的加工技术，(2)研究和实施集成肖特基传感器的硅膜基微机械晶片上探头，以及(3)用于与基于异质集成的测试和测量仪器集成的紧凑、高阶太赫兹倍频源的研究和原型制作。研究实现这种集成的工艺具有内在的智力优势，本提案的主要工作致力于研究制造高性能太赫兹电子传感器的方法，该传感器具有机械坚固的主机基板，可直接与物理接触接口，而不需要夹具。太赫兹器件设计、制造技术和计量的基本问题将在这项工作中解决，目的是实现新的和先进的仪器，允许进行目前不可能或不可行的测量。

The terahertz (or submillimeter-wave) region of the electromagnetic spectrum has long been understood as crucial to fundamental scientific inquiry and progress in fields such as radio astronomy, atmospheric physics, and remote sensing. Moreover, new and emerging device concepts promise to open this largely-inaccessible spectrum to further scientific study as well as important applications in imaging, non-destructive test and evaluation, and high-bandwidth communications. Unfortunately, the infrastructure and measurement tools needed to develop these new technologies remain severely limited. Current approaches to realizing measurement instrumentation at submillimeter wavelengths are based largely on a modular approach using waveguide interfaces. This results in fully-assembled measurement apparatus with considerable geometric footprint that can prove unwieldy or unsuitable for many important scenarios, for example in situations when the device or system to test must be maintained within a shielded enclosure such as a vacuum chamber or cryostat. This project is focused on addressing this critical issue through the development of compact and low-profile measurement instruments that are based on high-performance terahertz sensors heterogeneously integrated with micromachined support membranes that allow direct-contact in situ characterization of planar devices and systems at terahertz frequencies. As a consequence, this work will have broad impact on the growing terahertz research community through the availability of new and advanced metrological instrumentation that permit measurements that presently are not possible or feasible. The creation of new measurement techniques and capabilities is fundamental to the advancement of science; scientific discovery and progress in engineering are predicated on the creation of instruments that open new physical domains for experimentation and inquiry. This work represents an initial, critical, and necessary step towards developing instruments that overcome the inherent drawbacks limiting current approaches to terahertz metrology.The goal and scope of this project is to advance the infrastructure for measurement and characterization of terahertz devices, components, and systems through the development of instrumentation technologies that are based on heterogeneous integration. The research pursued focuses on heterogeneous integration across materials systems (e.g., III-V semiconductors and silicon) and across physical domains (e.g., electronics and mechanics). Towards this end, the specific approach to be undertaken includes three primary thrusts: (1) development of processing technologies for low-parasitic terahertz Schottky diode sensors heterogeneously integrated onto thin silicon membranes, (2) investigation and implementation of silicon membrane-based micromachined on-wafer probes incorporating integrated Schottky sensors, and (3) research and prototyping of compact, high-order terahertz frequency multiplier sources for integration with test and measurement instrumentation based on heterogeneous integration. There is inherent intellectual merit in researching processes that enable such integration and a significant effort of this proposal is dedicated to investigating methods that permit fabrication of high-performance terahertz electronic sensors with mechanically-robust host substrates amenable to direct, physical contact interfaces without need for fixturing. Fundamental issues of terahertz device design, fabrication technology, and metrology will be addressed during this work with the aim of realizing new and advanced instrumentation that permit measurements that presently are not possible or feasible.