Thermally Efficient GaN Devices for High Performance Microwave Amplifiers

在过去的十年中，在基于氮化镓（GaN）的高电子迁移率晶体管（HEMT）的开发中已经做出了显著的努力。这已经证明了这项技术的明显优势，GaN基电子器件的功率密度比砷化镓（GaAs）生产的器件高出5倍。还表明，与传统的基于GaAs的产品相比，这种高功率密度可以换取提高的效率或增加的总功率。然而，更高的功率密度也意味着器件中每单位面积的废热能更高，并且在没有有效去除废热能的情况下，导致器件在高沟道温度下操作，这都降低了器件性能和可靠性。事实上，当今的GaN器件受到热限制，并且必须显著降低额定值以将沟道温度限制在200摄氏度以下，以改善RF性能并显著改善平均故障时间（MTTF）。尽管如此，现在也很清楚，GaN基RF晶体管将成为许多未来应用的微波技术选择。事实上，GaN放大器已经为基站、工业科学和医疗以及航空航天和国防应用提供了无与伦比的性能，但需要改进热管理才能获得这些好处。目的和目标：本项目旨在开发在高热导率碳化硅（SiC）衬底上生长的热增强GaN基HEMT RF电子器件。1）设计、制备和表征具有集成热通路的小栅周GaN基HEMT器件，其具有：a）大于20 W/mm的功率密度和B）单位电流增益和功率增益电流截止频率大于50 GHz;以及2）具有每个器件能够提供10 - 100 W RF功率的大栅极外围的器件的实现和表征。研究方法的新奇：在这个项目中，将研究各种热管理策略，包括使用集成热通孔和分布式栅极设计。初步的实验和模拟结果表明，器件性能的显着改善，可以实现。利用负载牵引和S参数测量的器件特性将为技术优化提供所需的反馈。与EPSRC的战略和研究领域相一致：研究主题与EPSRC的RF和微波器件、非CMOS器件技术和未来制造的优先领域相一致。其潜在应用和好处：随着世界越来越依赖无线通信和雷达系统，RF和微波应用变得越来越重要。RF GaN晶体管有可能成为这些领域中推进系统的RF使能技术;具有改进的热管理的GaN器件将进一步加速这些发展。根据您阅读的市场报告，RF和微波元件行业估计为10亿美元，其中40%的设备用于通信基站。工业和新兴商业市场将使用这些晶体管，例如用于工业过程的高流明照明，建筑设计，舞台和体育场，工业/家用高效加热以及医疗辐照。

Over the last decade a significant effort has been made in the development of Gallium Nitride (GaN) based High Electron Mobility Transistors (HEMTs). This has resulted in the demonstration of clear benefits of this technology with GaN based electronic devices offering up to 5 times higher power density than devices produced in Gallium Arsenide (GaAs). It has also been shown that this high power density can be traded for improved efficiency or increased total power compared to conventional GaAs based products. The higher power density, however, also means that waste heat energy per unit area in the devices is higher and without its efficient removal results in devices operating at high channel temperatures, which both degrades the device performance and reliability. Indeed, today's GaN devices are thermally limited and have to be significantly de-rated to limit channel temperatures to under 200 degC for improved RF performance and a significantly improved mean-time-to-failure (MTTF). Nonetheless, it is now also clear that GaN based RF transistors will be the microwave technology of choice for many future applications. Indeed, GaN amplifiers already offer unparalleled performance for base stations, industrial scientific & medical, and aerospace & defence applications, but improvement in thermal management is required to reap the benefits.Aims and objectives:This project seeks to develop thermally enhanced GaN-based HEMT RF electronic devices grown on the high thermal conductivity Silicon Carbide (SiC) substrates. It has the following objectives: 1) Design, fabrication and characterization small gate periphery GaN-based HEMT devices with integrated thermal pathways and with: a) a power density of over 20 W/mm and b) unity current gain and power gain current cut-off frequencies in excess of 50 GHz; and 2) Realization and characterisation of devices with large gate periphery capable of delivering 10 - 100 W RF power per device.Novelty of the research methodology:On this project, various thermal management strategies including the use of integrated thermal vias and distributed gate designs will be investigated. Preliminary experimental and simulation results indicate that significant improvements in device performance can be achieved. Device characterisation using load pull and S-parameter measurements will provide the feedback required for technology optimisation.Alignment to EPSRC's strategies and research areas:The research topic is aligned to EPSRC priority areas of RF and Microwave Devices, Non-CMOS Device Technology and Manufacturing the Future.Its potential applications and benefits:RF and microwave applications are becoming increasingly important as the world becomes more reliant upon wireless communications and radar systems. RF GaN transistors have the potential to be the RF enabling technology for advancing systems in these sectors; GaN devices with improved thermal management will further accelerate these developments. Depending on which market report you read, the RF and microwave components sector is estimated at $1 billion dollars, with 40% of devices purchased for communications base stations. Industrial and emerging commercial markets will use these transistors for example in high lumen lighting for industrial processes, architectural design, stage and stadia, industrial/domestic high-efficiency heating, as well as medical irradiation.