EAGER: Formative Research on Contacts to Gallium-Oxide for Electronic and Optoelectronic Devices

标题：氧化镓半导体材料和界面形成研究计划加速超高效电子产品的发展非技术：全球能源危机使开发用于能量转换和传输的超高效电子设备变得迫切。电力占美国一次能源消耗的三分之一以上，其中很大一部分是由电力电子处理的。例如，电力电子需要在电网内进行有效的电力开关，以及混合动力电动汽车的电源和海军舰船平台的电力转换器，以及将可再生能源系统整合到电网中。在这些应用中，除了系统的大小和成本外，电力半导体器件也是决定能量转换效率的关键部件。由于其最新的材料(晶体)可获得性和其极端的性质，氧化镓(Ga2O)是一种新型的半导体材料，有望产生用于超高效率电子器件的优异器件。尽管美国对氧化镓有着浓厚的兴趣，但迄今为止，绝大多数氧化镓的研发(R&A；D)都是在日本进行的。该研究项目旨在加快基于氧化镓材料和界面的超高效电子设备(尤其是电力设备)的发展，并为美国国内的氧化镓研发活动奠定基础。最终，电力电子的进步将带来节能和相关碳排放的大幅减少。作为该项目的一部分，研究生和本科生将接受培训，发展在半导体行业工作所需的专业技能。其他成果将包括面向初中生和教师的科学宣传，以及向这一新兴领域提供信息和帮助建立研发活动的会议。技术：具体地说，在这个项目中，卡内基梅隆大学的研究人员将进行一项形成性研究，重点是物理、化学和工艺条件，这些条件决定了掺杂的Ga2O_3单晶衬底和外延层的电接触行为。已经展示了许多基于Ga2O3的器件，包括肖特基二极管、MESFET和MOSFET。然而，由于Ga2O_3作为宽禁带半导体的研究还处于非常早期的阶段，人们对如何控制这种材料的器件相关界面还知之甚少。具体地说，这项研究将集中在(1)形成低电阻率欧姆接触，通过热力学计算和考虑其他物理和化学性质，以及(2)表征不同晶体取向的多种金属的肖特基二极管，并将肖特基势垒高度与预测值进行比较。了解金属功函数、晶体取向、界面反应和工艺条件对接触性能的影响将成为一个平台，使设备工程师能够进行知情设计，以实现基于Ga2O3的优化器件，并可能在未来基于(Al，Ga，In)203材料的合金和异质结构。

Title: Formative Research Program on Gallium Oxide Semiconductor Materials and Interfaces to Hasten the Development of Ultra-High Efficiency Electronics Non-Technical:The global energy crisis presents an urgency to develop ultra-high efficiency electronics for energy conversion and transport. Electricity accounts for more than a third of primary energy consumption in the U.S., and a large portion of that electricity is handled by power electronics. For example, power electronics are required for efficient electrical switching within the electrical grid, as well as for power supplies in hybrid electric vehicles and for power converters in Naval ship platforms and to integrate renewable energy systems into the electrical grid. In each of these applications, the power semiconductor device is the critical component that determines the energy conversion efficiency, in addition to the size and cost of the system. Because of its recent material (crystal) availability and its extreme properties, gallium oxide (Ga2O3) is a novel semiconductor material that is expected to yield superior devices for ultra-high efficiency electronics. Although there is strong interest in the U.S., to date, the vast majority of research and development (R&D) on gallium oxide has been conducted in Japan. This research project is designed to hasten the development of ultra-high efficiency electronics (especially power devices) based on gallium-oxide materials and interfaces and to establish a foundation for R&D activities on gallium-oxide within the U.S. Ultimately, advances in power electronics will account for substantial gains in energy savings and an associated reduction in carbon emissions. As part of this program graduate and undergraduate students will receive training and develop professional skills needed to work in the semiconductor industry. Additional outcomes will include scientific outreach to middle and high school students and teachers, and conference sessions to inform and to help build R&D activities in this emerging field. Technical:Specifically, in this project researchers at Carnegie Mellon University will conduct a formative study focusing on the physics, chemistry, and processing conditions that determine the behavior of electrical contacts to doped Ga2O3 single crystal substrates and epitaxial layers. A number of devices based on Ga2O3, including Schottky diodes, MESFETs, and MOSFETs, have been demonstrated. However, as research on Ga2O3 as a wide bandgap semiconductor is in its very early stages, there is little understanding of how to control device relevant interfaces to this material. Specifically, this research will focus on (1) forming low resistivity ohmic contacts, informed by thermodynamic calculations and consideration of other physical and chemical properties, and (2) characterizing Schottky diodes for a wide range of metals on different crystal orientations of Ga2O3 and comparing the Schottky barrier heights with predicted values. Knowledge of the effects of metal workfunctions, crystal orientation, interfacial reactions, and processing conditions on the contact properties will serve as a platform to enable informed designs that device engineers can use to achieve optimized devices based on Ga2O3, and, potentially, on alloys and heterostructures of (Al,Ga,In)2O3 materials in the future.