CAREER: A New GaN-based Unit Cell for Highly Efficient Integrated Power Conversion

该学院早期职业发展(Career)计划奖项的研究目标是开发一种具有集成驱动电路的超低损耗功率晶体管，用于功率转换应用。该方法将使用一种创新的制造工艺来解决氮化镓垂直晶体管的问题，这些问题以前限制了该技术实现卓越的性能和广泛采用。由于低效的电力转换，大量的能源被浪费为热量。通过该方案提供的解决方案将减少或消除浪费的能源，从而有效地延长可用能源的寿命。这种节能将增加全球能源安全，减少温室气体排放。教育和宣传部分旨在培养人们对科学、技术、工程和数学(STEM)学科的兴趣，并发展本科生和K-12阶段的科学知识。这些活动的重点是与不同的学生群体合作，特别是妇女和其他代表性不足的群体。研究和教育的整合将通过研讨会和课程来实现，这些研讨会和课程致力于了解半导体器件，并为他们的K-12课堂建立原型或模型。具体的外展目标包括通过工程探险与K-8女孩合作，通过为教育服务的工程师与师范学院候选人合作。教育目标是继续在最近引入的电力电子课程的基础上，扩展通过该计划下的研究获得的尖端技术知识。氮化镓的氮极性取向的独特极化特性将首次用于开发在结构生长过程中不需要中断的垂直晶体管。氮化镓/氮化镓异质结的反向极化场被设计为阻止晶体管中的电流，同时为电流在指定区域内的流动提供非常导电的路径。根据这种新颖的晶体管设计，估计导通电阻低于1 mhm.cm2，并将其设置为本程序的目标。由于电路板互连和焊线电感的不利影响，缺乏集成的栅极驱动器限制了功率转换器的高开关速度和效率。这一创新首先开发了氮化物垂直晶体管的卓越性能，然后通过集成基于片内横向晶体管的驱动电路，消除了通过键合导线和板互连的迹线电感对开关速度施加的限制，从而将电力电子设备的限制推到了非常高的功率密度和高频下提供的高效率。这项研究的范围扩展到基础器件研究和应用领域，在那里器件结构将被用来确定材料的基本性质，包括第一次直接测量氮化镓中的电子速度。最后，这种优势将通过新的电路架构显现出来，新的电路架构通过在高频下实现高效率的功率转换来提高效率和降低外形因数。

The research objective of this Faculty Early Career Development (CAREER) Program award is to develop a very low loss power transistor with an integrated drive circuit for power conversion applications. The approach will use an innovative fabrication process to address issues with Gallium Nitride-based vertical transistors that have previously limited the technology from achieving superior performance and widespread adoption. A significant amount of energy is wasted as heat due to inefficient power conversion. The solution provided through this program will reduce or eliminate the wasted energy thereby effectively extending the lifetime of available energy resources. This energy savings will add to the global energy security and reduce greenhouse gas emissions. The educational and outreach components are aimed at fostering interest in Science, Technology, Engineering, and Mathematics (STEM) disciplines and developing scientific knowledge at the undergraduate and K-12 levels. These activities are focused on working with a diverse group of students particularly women and other underrepresented groups. Integration of the research and education will be achieved through workshops and classes dedicated to understanding semiconductor devices and build prototypes or models for their K-12 classrooms. Specific outreach goals include collaboration with K-8 girls through Engineering Adventure and Teacher College candidates through Engineers Serving Education. The educational goal is to continue building on a recently introduced coursework on power electronics and extend the knowledge on cutting edge technologies acquired through the research under this program.The unique polarization properties of the nitrogen polar orientation of Gallium nitride will be utilized for the first time to develop vertical transistors that require no interruptions during the growth of the structure. The reverse polarization field of the Aluminum Gallium Nitride/Gallium Nitride heterostructure is designed to block current in the transistor while providing a very conductive path for the current to flow in designated region. An on-state resistance below 1 mohm.cm2 is estimated from this novel transistor design and is set as a target in this program. Lack of an integrated gate driver has limited high switching speed and efficiency of power converters due to the deleterious effects of board interconnects and bond wire inductance. This innovation pushes the limits of power electronics to very high power densities with high efficiency delivered at high frequencies by first developing superior performance of nitride-based vertical transistors and then eliminating the limits placed on switching speed by trace inductance of bond wires and board interconnects by integrating the driver circuit based on lateral transistors on-chip. The scope of this research extends into both fundamental device research and application space where the device structures will be used to determine fundamental properties of the material including the first direct measurement of electron velocity in Gallium nitride. Finally the merit will be evident through new circuit architectures with increased efficiency and reduced form factor by enabling high efficiency power conversion at high frequencies.