III族氮化物半导体材料与器件的辐照损伤的同步辐射X射线研究

In early 2012, Russia's Mars explorer suffered failure because of a computer malfunction caused by the impact of cosmic rays. During Fukushima nuclear crisis in Japan in 2011, intelligent robots failed to be sent into the nuclear power plant to handle the leakage due to the high-dose irradiation damage to the electronics. These sorts of events indicate the crucial role played by the anti-irradiation capability of semiconductor materials and devices on their dependability and effective lifetime. So far most studies have been carried out following a research route from irradiation experiment to performance measurment,and the studies from the standpoint of observing (point) defect structure are rare. In order to master irradiation effects on III-nitride semiconductor materials and devices, we propose to investigate the generation, structure and evolvement rules of defects under different irradiation conditions using synchrotron radiation x-rays methods mainly based on diffuse x-ray scattering and x-ray absorption fine structure spectroscopy, and to measure the corresponding optic and electric properties. This study is expected to reveal the irradiation parameters - - defect structure - - photoelectric properties relation. It would provide new clues for the defect theory development of wide-bandgap compound semiconductors. It will play an important role in understanding and evaluating the irradiation damage to III-nitride semiconductor materials and devices as well as in enhancing their dependability. This research will provide fundamental reference for the design of related photoelectronic devices and their irradiation protection used in our nation's space tasks.

2012年初俄罗斯的火星探测器因宇宙线辐射导致计算机系统失灵而失败，2011年日本福岛核电站事故因为辐射损伤而未能使用机器人来检查清理，这类事件表明，半导体材料和器件的抗辐照损伤能力对其在辐照环境中应用的可靠性和有效寿命至关重要。迄今相关研究主要是循着辐照试验－性能测试的研究路线来开展，而从直接观测（点）缺陷结构的角度来研究辐照损伤效应的工作很少见。为了从缺陷结构方面弄清III族氮化物半导体材料和器件的辐照效应，我们拟采用以同步辐射X射线漫散射为核心的X射线方法研究它们在不同辐照条件下点缺陷的产生、结构及其变化规律，测量出对应的宏观性能，找出辐照参数－缺陷结构－光电性能之间的对应关系。该研究将为宽禁带化合物半导体的缺陷理论发展提供新的实验线索，对理解和评估III族氮化物材料与器件的辐照损伤、提高其可靠性有重要的作用，也将为我国的空间用相关光电子器件及其辐射防护的设计提供基础依据。

在本面上基金的支持下，我们开展了III-族氮化物半导体材料GaN-AlN-InN体系与HEMT器件的辐照损伤研究，并把高能离子注入的GaN和ZnO单晶样品进行了研究对比。我们首先采用高能As离子注入技术制备了GaN和ZnO辐照样品，随后在北京同步辐射装置上采用黄昆漫散射（HDS）方法测量点缺陷的结构及其在退货前后的变化，我们也尝试采用扫描微区衍射成像技术对缺陷进行成像研究，为此我们编写了其数据的图像重建软件，但该实验手段因分辨率很低而没有提供有用的缺陷结构信息；我们继续在北京同步辐射装置上采用了同步辐射X射线黄昆漫散射、衍射（XRD）和反射（XRR）测量了高能As离子辐照的GaN和ZnO单晶样品，获得了样品中点缺陷的尺寸、分布对称性和退火后的迁移和聚集情况以及相应的电输运性质和形貌的变化研究，分析出注入后p型电导的来源；对HEMT（GaN-AlGaN-AlN-uGaN-Fe-doped GaN-AlN缓冲层/Al2O3衬底）进行了辐照前的X射线和霍尔效应研究。在研究中，为了解决漫散射信号弱、同步机时少这两个困难，我们在该研究需求的推动下在BSRF-1W1A漫散射实验站上建成了Spec-EPICS-Pilatus-Autofilter联用系统，通过发展该二维面探测及其全自动保护系统大大提高了晶体倒易空间绘制的效率；为了增加探测点缺陷在晶格中位置的印证手段，我们又发展了X射线驻波（XSW）方法，先后完成了多层膜样品和单晶样品的测试实验，这两种技术刚刚完成，将极大的提高我们的和用户的实验效率。