Collaborative Research EAGER: Reliable High Current Density Vacuum Electronics

真空电子器件和系统以控制电子在真空中的运动为基础，有许多应用，包括等离子体显示器、用于通信和成像的微波和太赫兹辐射源、扫描电子显微镜和用于极端环境的电子学。然而，由于低电流密度和低可靠性，高效可靠地将电子发射到真空中的设备一直是具有挑战性的。该项目是普渡大学和俄亥俄州立大学的合作项目，旨在展示真空发射器的新设计，使其能够在高电流密度下可靠运行。将使用两种不同的半导体-硅和氮化镓-的两种互补方法来演示真空发射器，并以详细的电子和热建模技术为指导。这项拟议的工作将使高性能真空电子器件能够实现微米级的半导体芯片集成。这些微型高电流密度发射器将超过当前最先进的技术水平，并可以实现大量利用真空电子设备进行显示、高数据速率通信、高温电子和成像的新应用。该项目将在半导体技术的一个高度跨学科和新领域对研究生进行培训和教育，并可能导致真空电子电路和系统的几个新的商业应用。这个合作项目将结合普渡大学在硅制造和真空电子学方面的互补专业知识，以及俄亥俄州立大学的III-氮化物异质结构和极化工程，以展示可靠的高电流密度发射器。为了利用硅中载流子浓度较低的电流饱和效应，研究一种新的硅场发射器件，它将通过晶格和电离杂质散射限制输运来控制电流密度。利用异质结构和极化工程的并行方法将在平面III-氮化物半导体结构中实现高效的场发射。III-氮化物半导体具有本征极化，使大电压可以跨越纳米级距离下降。这使得现场工程人员能够将半导体内部的导带与外部的真空水平对准。极化工程概念将与超尺度结构中的弹道传输相结合，以实现III-氮化物半导体表面的高效场发射。所提出的器件将在平面几何结构中实现高电流密度场发射，这可能对多种应用有利。普渡大学和俄亥俄州立大学将开发复杂的建模技术，包括异质结构中输运的二维电热模拟和蒙特卡罗模拟，以设计和评估硅和III-氮化物材料系统中的真空发射体。开展集成真空电子器件微细加工技术的开发和示范工作。拟议的工作将有助于更好地理解工程纳米级结构和III-氮化物半导体的场发射。这里提出的概念使用了有前途的和新颖的方法来克服与高电流密度发射体相关的挑战，因此可能对真空微电子的科学和应用产生革命性的影响。

Vacuum electronic devices and systems, which are based on the control of electron motion through vacuum, have numerous applications including plasma displays, microwave and terahertz radiation sources for communications and imaging, scanning electron microscopes, and electronics for extreme environments. However, devices that efficiently and reliably emit electrons into vacuum have been challenging due to their low current density and poor reliability. The proposed project, a collaboration between Purdue University and Ohio State University, aims to demonstrate new designs for vacuum emitters to enable them to operate reliably at high current densities. Two complementary approaches involving two different semiconductors - Silicon and Gallium Nitride will be used to demonstrate vacuum emitters, guided by detailed electronic and thermal modeling techniques. The proposed work will enable realization of high-performance vacuum electronic devices that can be integrated on semiconductor chips at the micrometer scale. These microscale high current density emitters would surpass the current state-of-art and could enable a large array of new applications that exploit vacuum electronics for display, high data-rate communications, high-temperature electronics, and imaging. The project will lead to training and education of graduate students in a highly interdisciplinary and novel area of semiconductor technology, and could lead to several new commercially relevant applications for vacuum electronic circuits and systems.This collaborative project will combine the complementary expertise in Si fabrication and vacuum electronics at Purdue University, and III-nitride heterostructure and polarization engineering at Ohio State University to demonstrate reliable high current density emitters. A new approach to Si field emitters will be investigated to take advantage of current saturation effects in Silicon with fairly low carrier concentration, The Si emitters will be designed to control current density through lattice and ionized impurity scattering limited transport. A parallel approach using heterostructure and polarization engineering will be pursued to achieve highly efficient field emission in planar III-nitride semiconductor structures. III-nitride semiconductors have intrinsic polarization that enables large voltages to be dropped across nanometer scale distances. This enables field engineering to align the conduction band within the semiconductor with the vacuum level outside. The polarization engineering concepts will be combined with ballistic transport in ultrascaled structures to achieve efficient field emission from III-nitride semiconductor surfaces. The proposed device will enable high current density field emission in planar geometries that could be advantageous for several applications. Sophisticated modeling techniques including 2-dimensional electro-thermal simulations and Monte Carlo simulations of transport in heterostructures will be developed at Purdue University and Ohio State University to design and evaluate the vacuum emitters in both Silicon and III-nitride material systems. Development and demonstration of micro-fabrication technology for integrated vacuum electronic devices will be done. The proposed work would lead to better understanding of field emission from engineered nanoscale structures and III-nitride semiconductors. The concepts proposed here use promising and novel approaches for overcoming challenges related to high current density emitters, and could therefore have transformative impact on the science and applications of vacuum microelectronics.