GOALI: III-Nitride and SiC Transistors for High-Frequency, High-Power Devices

某些宽带隙半导体材料正迅速成为重要器件应用的首选材料。这些应用包括紫外（UV）光电探测器、蓝光和紫外光发射器以及高频、大功率电子器件。在这种背景下，氮化镓和相关的iii -氮化物材料最近引起了极大的兴趣，并且已经做了许多旨在评估其基本性质的工作。在过去的NSF资助下，佐治亚理工学院和明尼苏达大学的小组参与了这项提议，他们开始合作开发一种新颖的、基于材料理论的设备建模技术。将该技术应用于GaN块体材料的研究，获得了许多新的信息：首次确定了高场载流子漂移速度，首次确定了空穴输运性质，首次确定了电子和空穴碰撞电离率，首次确定了GaN中的击穿电场，以及A1N和AlGaN的低场和中场电子输运性质。在这些成就的基础上，现在可以对GaN和相关III-N材料在几种不同应用中的潜力进行更面向器件的研究。这项研究的主要目标是分析用于高频功率放大器的III-N材料和SiC的说明书。该计划包括理论和建模工作与实验计划相结合。提出的理论和建模工作将辅以实验，以帮助完善和比较模型与实际结构。通过与实验团队合作，可以在一个关键的反馈机制的存在下，从理论上探索材料中的位错和杂质等非理想性的影响，这将提高理论模型的准确性和相关性。此外，理论和建模工作将探索新的物理效应可以用来提高器件性能的方法。具体来说，该模型将研究压电感应电荷密度的使用，以增加异质结场效应晶体管的载流能力，以及如何增加异质结构双极晶体管基极内的p型载流子浓度，以降低基极电阻。此外，该理论和模型将用于确定基于SiC和GaN的高频高功率放大器的性能极限，通过提供影响其性能的参数（即击穿场，载流能力，“膝”电压和散热）的首次准确确定。对不同FET设计的击穿特性的研究将建立在我们早期在大块GaN材料中的冲击电离工作的基础上。然而，它将不仅仅局限于理想的块状材料，还将包括实际器件结构中场不均匀性的影响，以及与杂质和位错有关的对击穿特性的影响。对于有意义的器件建模工作，需要与实验工作紧密耦合。这将通过与活跃于III-N和SiC研究的三个实验组的广泛合作来完成。这项工作的主要合作者是卓越真空技术协会。（SVTA），该公司生产最先进的III-N材料和设备。多年来，Ruden教授与SVTA在这一领域进行了密切而富有成效的互动。SVTA将按制造成本为该计划提供设备质量III-N结构。第二个关键合作团队位于摩托罗拉位于亚利桑那州坦佩的总部。摩托罗拉团队将主要参与高频设备测试。最后，瑞典查尔姆斯大学的Willander教授小组将提供SiC材料，并将积极参与SiC和III-N器件的制造和表征。因此，可以将计算结果与实验结果进行直接比较，极大地帮助了模型的改进，并确保它们解决了在最先进的设备中所面临的问题。与拟议项目相关的主要研究人员的其他合作包括霍尼韦尔公司、洛克希德马丁公司（III-N设备）和北电公司（SiC设备）。＊＊＊

9811366 Ruden Certain wide band gap semiconductor materials are quickly emerging as the materials of choice for important device applications. Among these applications are ultraviolet (UV) photodetectors, blue and UV light emitters, and high frequency, high power electronic devices. In this context, GaN and the related III-nitride materials have recently attracted great interest, and much work has been done aimed at assessing their basic properties. In a past NSF sponsored effort, the Georgia Tech and University of Minnesota groups involved in this proposal have teamed to begin the development of a novel, materials theory based device modeling technique. Application of this technique to the study of GaN bulk material has resulted in much new information: the first determination of the high field carrier drift velocities, the first determination of the hole transport properties, the first determination of the electron and hole impact ionization rates, the first determination of the breakdown electric fields in GaN, and the low and intermediate field electronic transport properties of A1N and AlGaN. Building on these achievements, a more device oriented study of the potential of GaN and the related III-N materials for several different applications can now be made. It is the principal goal of this proposed research effort to analyze the prospectus of the III-N materials and of SiC for use in high frequency power amplifiers. The program involves a theory and modeling effort in conjunction with an experimental program. The proposed theory and modeling work will be complemented by experiment in order to help refine and compare the models to real structures. By working in conjunction with an experimental team, the effect of nonidealities such as dislocations and impurities within the materials can be explored theoretically in the presence of a crucial feedback mechanism that will enhance the accuracy and relevance of the theoretical models. In addition, the theory and modeling effort w ill explore ways in which novel physical effects can be used to improve device performance. Specifically, the modeling will examine the usage of piezoelectrically induced charge densities to increase the current carrying capability of a heterojunction field effect transistor and how the p-type carrier concentration within the base of a heterostructure bipolar transistor can be increased to reduce the base resistance. In addition, the theory and modeling will be used to determine the ultimate limits of performance of SiC and GaN based high frequency, high power amplifiers by providing the first accurate determination of the parameters which influence their performance, i.e., the breakdown field, current carrying capability, "knee" voltage and heat dissipation. The study of the breakdown characteristics of different FET designs will build on our earlier work on impact ionization in bulk GaN material. However, it will not be limited solely to ideal bulk material but will include the effect of field non-uniformity in realistic device structures as well as effects associated with impurities and dislocations on the breakdown properties. For a meaningful device modeling effort close coupling to experimental work is desirable. This will be accomplished through extensive collaboration with three experimental groups active in III-N and SiC research. The principal collaborators in this effort are Superior Vacuum Technology Assoc. (SVTA) of Eden Prairie, MN, which has produced state of the art III-N materials and devices. Prof. Ruden has had close and fruitful interaction with SVTA in this area for several years. SVTA will provide device quality III-N structures for this proposed program at cost of fabrication. The second key collaborative group is at Motorola in Tempe, AZ. The Motorola group will be principally involved in high frequency device testing. Lastly, Prof. Willander's group at Chalmers University, Sweden, will provide SiC material and will be strongly involved in the fabrication and characterization of both SiC and III-N devices. Direct comparison of the calculations to experiment can thus be made, greatly aiding the refinement of the models and ensuring that they address issues confronted in state of the art devices. Additional collaborations of the principal investigators relevant to the proposed program involve the Honeywell Corp., Lockheed Martin Corp. (III-N devices), and Nortel(SiC devices). ***