基于二维石墨烯的GaN-HEMT外延结构生长和器件剥离研究

与高热导率的金刚石结合是目前解决大功率电子器件散热难题的最有效方案，也是电子器件领域的研究热点。但GaN-HEMT器件从衬底上剥离困难及剥离过程中缺陷的引入，限制了金刚石的高热导率优势在大功率GaN-HEMT器件应用中的充分发挥。本项目拟以GaN在SiC/石墨烯上的外延生长作为研究突破点，借助石墨烯与外延层和衬底之间的范德瓦尔斯力，实现GaN-HEMT器件从衬底上的无损剥离。首先，调控石墨烯上氮化物的成核、合并和生长模式，研究外延层中缺陷运动及其与应力的相互作用机制；其次，将外延层图形化，探明衬底/外延层之间的作用力在片内不均匀分布对剥离过程的影响；最后，研究剥离后应力弛豫对器件性能和可靠性的主要影响及机理。最终实现高质量GaN-HEMT外延结构的生长和器件的无损剥离，为其与金刚石结合铺平道路，为GaN-HEMT在5G通信和远距离雷达探测领域的应用奠定基础。

Combining high power GaN-based electronic devices with high thermal conductive diamond can effectively solve the difficulty of heat dissipation, thus has been attracting much attention. However, due to the difficulties and defects involved in the lift-off process, the advantage of high thermal conductivity of diamond in the application of high power GaN-HEMT is limited. We intend to grow GaN on graphene in order to realize the harmless lift-off of GaN-HEMT aided by the van der Waals forces between graphene and substrate as well as epilayer. Firstly, we will investigate the interactions between defects and stress in the epilayer by adjusting the nucleation, coalescence and growth mode of nitrides on graphene. Then, in order to lift-off the epilayer on wafer-scale, the epilayer will be patterned and the effect of bonding configuration between epilayer and substrate on the lift-off process will be studied. Lastly, after lift-off, we will explore the effects of strain relaxation on the devices performance and reliability as well as the underling mechanisms. Through above work, we aim to achieve the growth of high quality epilayer and the harmless lift-off of GaN-HEMT, which will promote the development of integrating GaN-HEMT on diamond and its applications for 5G communications and long-range radar detection.