AlGaN/GaN MIS-HEMT器件在质子辐射下的退化机理，寿命预测模型与加固技术研究

Due to the significant advantages, AlGaN/GaN MIS-HEMTs have received much attention in space environment applications. However, critical issues still need to be solved for reilable operation in space applications. In this project, the degradation mechanism of AlGaN/GaN MIS-HEMTs under proton radiation, the characteristics of defects, lifetime prodiction model and anti-radiation hardening techniques will be researched in-depth, based on our provious study in this research area. By studying the relationship between defect generation and electrical parameters degradation for MIS-HEMTs under proton radiation, the key factors that affects device performance will be discovered. Considering the effects of materials growth process, device structures and electrical stress, the degradation mechanism of AlGaN/GaN MIS-HEMTs under proton radiation can be identified. For the main defects that induces device degradation, the basic physical characteristics will be studied in-depth, considering of the effects of temperature and electric field on the device degradation. This work can provide valuable information for MIS-HEMTs modeling, lifetime prediction, etc. Finally, great efforts will be made to explore the key and most sensitive factors that affect the device degradation, and lifetime prediction model will be successfully built. Condering of the main defects that induces device breakdown, the anti-radiation hardening techniques will be propsoed and verified.The research achievements in this project will have great impact on the improvement of long-term reliability of GaN based MIS-HEMTs in proton radation environments, and lay a consolidate foundation for MIS-HEMTs in space applications.

本项目针对典型AlGaN/GaN MIS-HEMT器件在空间环境中的广阔应用前景和现实中面临的主要问题，基于前期研究基础，深入开展了包括器件在质子辐射下的失效机理、缺陷的基本物理特性及寿命预测模型与加固技术等三方面的研究。通过研究质子辐射下缺陷的产生与器件电学参数退化之间关系，找出影响器件性能的最主要因素，结合材料生长、器件结构、电应力等对器件退化的影响，最终确定了MIS-HEMT器件在质子辐射下的主要退化机理。针对引起退化的主要缺陷，对其基本物理特性以及温度、电场下的退火特性开展了深入研究，为器件建模等提供信息。在此基础上，从诸多因素中找出与失效相关的关键失效敏感因素，建立辐射环境下的器件寿命预测模型；围绕器件退化相关的主要缺陷，从材料及器件角度分别提出抗质子辐射加固理论并进行实际验证。相关研究成果为GaN基MIS-HEMT器件在空间质子辐射环境中长期可靠性的提高提供理论指导与技术支撑。

本项目针对典型氮化镓器件在空间质子辐射环境中面临的可靠性问题开展了系统研究，具体包括失效机理、缺陷的基本物理特性变化及寿命预测模型与加固技术等三方面。首先，开展了仿真研究，获得了质子辐射对器件影响的基本规律。进一步，分析了3MeV，5×1014H+/cm2质子辐照对体陷阱和界面态的影响。在3MeV，5×1014 H+/cm2质子辐照后，通过电容-电压测试发现平带电压正向漂移0.3V。基于此，提取了载流子浓度随器件深度的分布。通过理论计算验证了AlGaN势垒层内的陷阱的去载流子效应是导致平带电压正漂的主因。更为重要的是，利用变频电导法首次分析了质子辐射对AlGaN/GaN异质结界面态的影响。提取时常数发现，它从辐射前的1.10-2.53μs增加到辐射后的3.46-37μs。同时，异质结界面态密度从9.45×1011~1.70×1013 cm-2•eV-1增加到1.8×1012~1.8×1013 cm-2•eV-1，激活能从0.34 eV~0.32 eV加深到0.41 eV~0.35 eV。通过研究质子辐射下缺陷的物理信息变化规律，进而找到缺陷与器件电学参数退化之间的关系。理论计算表明异质结界面态的库伦散射是导致器件迁移率退化的主因。分析了栅极/AlGaN界面态的影响，发现随着辐射剂量的增加，栅电极/AlGaN界面态的时常数、态密度与激活能均减小。这说明质子辐射有利于减小肖特基界面态密度，对于改善栅极界面是有利的。此外，还分析了3MeV，1×1014H+/cm2质子辐射对绝缘栅介质MIS-HEMT器件界面态的影响，发现MIS-HEMT器件界面态物理参数变化较小。在此基础上，开展了辐射环境下的器件寿命预测模型研究，并围绕引起器件退化的主要因素，从材料及器件角度分别提出抗质子辐射加固方法。相关研究成果可为氮化镓MIS-HEMT器件在空间质子辐射环境中长期可靠性的提高提供重要指导。