Semiconductor-based Terahertz Traveling Wave Amplifiers for Monolithic Integration

太赫兹（THz）放大器的单片集成可以为许多太赫兹系统的小型化和移动性铺平道路。在这个项目中，pi提出了一种新的太赫兹放大器配置，它可以使用行波现象学在半导体介质中提供太赫兹增益。行波增益的发生是由于移动的带电粒子和其附近的电磁波之间的同步相互作用。经典地，这种现象学提供了电磁波在大量的真空电子装置（如基于真空电子学的行波放大器）中的放大。值得注意的是，将这种现象转化为半导体介质并将其缩放到亚毫米尺寸是非常可取的。这是因为在微波单片集成电路（mmic）中可以获得类似的增益和高输出功率。该提案将解决新的计算算法、材料优化和器件配置创新，以基于半导体材料中的电子波动力学，在0.1至3太赫兹范围内创建高增益放大器拓扑。该项目旨在(1)引入有效的数值模拟工具来揭示半导体材料中电子-波相互作用的潜在复杂现象；(2)研究和验证利用同步电子-波相互作用进行太赫兹波放大的器件概念。总体而言，该项目将广泛影响医疗、安全和无线通信领域，并通过其对无线通信和成像技术的影响，使国家安全和国防弹性基础设施受益。该项目通过暑期实习项目培训和教育一名研究生和三名本科生，进一步支持劳动力发展。研究成果以及由此产生的新科学知识将与UNL的pi的课程开发相关联。该项目的具体科学创新将集中在多物理场、多尺度数值求解器、材料和器件配置创新以及通过制造和测量对放大器进行实验验证的进步上。为了达到优化的器件，pi利用高电子迁移率晶体管（hemt）和其他受限电子-气体系统中的自然受限二维电子气体来创建太赫兹电磁波的增益介质。这是通过增强二维受限介质附近的慢波结构来实现的，以提供电子-波相互作用和太赫兹波的放大。为了模拟这个问题，该项目将首先解决当前多尺度多物理场全球模型的低计算效率和准确性。项目将特别介绍时域数值求解器，它基于多域使用无条件稳定性来获得时间优势和迭代修正以保持精度。pi将采用交替方向隐式（ADI）和迭代ADI算法将其集成到多物理场有限不同时域方法中，以提供高达一个更高效的数值求解器。其次，该项目将使用所提出的求解器来开发行为模型、材料和几何优化，从而通过这些研究提供功率、增益和带宽的初步估计。数值研究将用于优化设备的制造和测量。在此背景下，本研究将广泛研究电磁慢波结构，对经典和新兴材料系统进行数值模拟，并提供新的器件概念，如使用2deg双分子层和超晶格。为了验证器件概念，提出了在ka波段进行冷试验，并提出了在w波段进行器件原型和测量。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Monolithic integration of terahertz (THz) amplifiers can pave way to miniaturization and mobility of many terahertz systems. In this project PIs propose a new configuration of terahertz amplifiers which can use traveling-wave phenomenology to provide terahertz gain in semiconductor media. Traveling wave gain occurs due to a synchronous interaction between moving charged particles and electromagnetic waves in its vicinity. Classically, this phenomenology has provided amplification of electromagnetic waves in a large array of vacuum electron devices (e. g. vacuum-electronics based travelling wave amplifier). Notably, translation of this phenomenon into semiconductor media and its scaling to sub-millimeter dimensions is highly desirable. This is because of the possibility of obtaining similar gains and a high output power within microwave monolithic integrated circuits (MMICs). This proposal will address new computing algorithms, material optimizations and device configuration innovations to create high gain amplifier topologies in 0.1 to 3 THz range based on electron-wave dynamics in semiconductor materials. This project aims at (1) introducing efficient numerical modeling tools to unveil the underlying complex phenomenology of electron-wave interactions in semiconductor materials and (2) investigating and validating the device concepts that exploit a synchronous electron-wave interaction for a THz wave amplification. Overall, the project will broadly impact the medical, security, and wireless-communication areas, and benefit the national infrastructure of security and defense resiliency through its impact on wireless communication and imaging technology. The project further supports workforce development through training and education of one graduate student and three undergraduate students via the summer internship program. The research outcomes as well as new scientific knowledge created from this proposal will be tied to the curriculum development by the PIs at UNL.The specific scientific innovations of the project will be focused on advancements of multiphysics, multiscale numerical solvers, material and device-configuration innovations, and experimental validation of the amplifier through fabrication and measurements. To reach an optimized device PIs exploit naturally confined 2D electron gas in high electron mobility transistors (HEMTs) and in other confined electron-gas systems for creating a gain media for terahertz electromagnetic waves. This is achieved by augmentation of slow-wave structures near 2D confined media to provide electron-wave interactions and amplification of THz waves. To model this problem, the project will first address the low computational efficiency and accuracy of current multiscale multiphysics global models. Project will specifically introduce time-domain numerical solvers that are based on multi-domain use of unconditional stability for gaining time-advantage and iterative corrections to maintain the accuracy. PIs will adapt Alternate Directional Implicit (ADI) and iterative ADI algorithm for their integration into multiphysics finite different time domain method to provide up to an order more efficient numerical solver. Secondly, the project will use the proposed solvers towards developing behavioral models, material, and geometry optimizations, and thus provide first estimates of power, gain, and bandwidth through these studies. Numerical studies will be used to optimize the devices for fabrication and measurements. In this context, the study will expansively investigate electromagnetic slow-wave structures, numerically model classical and new emerging material systems, and provide novel adaptation of the device concepts such as by using 2DEG-bilayer and superlattice. To validate the device concept, cold-tests are proposed in Ka-band, and device prototyping and measurements are proposed in W-band.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.