A Materials Research Diffractometer for High Resolution X-Ray Characterization of Group III Nitride Based Wide Band Gap Simiconductors

该奖项为III族氮基宽带隙半导体缺陷和应变的高分辨率x射线表征仪器提供了部分支持。将获得一个高分辨率的三轴材料研究衍射仪，能够测量x射线摇摆曲线和互易空间图。在这个装置中，一个三轴加上一个三反弹通道切割锗（220）分析仪晶体，将双轴衍射仪变成了三轴衍射仪，使其具有高分辨率。利用该衍射仪，可以将应变引起的面间距变化与位错等缺陷引起的倾斜区分开。因此，在一定的扫描模式下（w - 20扫描模式），即使有大量位错的薄膜的衍射峰也会很尖锐，并且可以准确地测量出峰的位置。这将提供比双晶衍射仪更精确的关于晶格参数、结构和材料应变的信息。此外，还可以分别得到衬底和薄膜的互反空间图，同时给出应变和缺陷的信息。这些高分辨率的发现对于开发新的小尺寸宽禁带半导体材料具有更少的缺陷和应变以及改善光电性能至关重要。要研究的材料系统用于光学和电子器件。利用由x射线高分辨衍射和x射线形貌技术组成的综合x射线衍射技术，对这些材料的结构、应变、成分、缺陷和极性进行分析。这些参数很重要，因为光电性能和器件性能强烈依赖于它们。将实验值与理论值进行比较，并建立模型来解释应变和缺陷。将根据这些模型向晶体种植者提出具体建议，并实现改进的器件制造。从而在氮基宽带隙半导体器件领域做出重大贡献。这项研究将与堪萨斯州立大学、曼哈顿、堪萨斯等地合作完成。这种衍射仪也将提供给威奇托州立大学和堪萨斯州其他大学的其他研究人员。目前在堪萨斯州还没有高分辨率的三轴衍射仪。材料研究已被确定为堪萨斯州的战略技术之一。所要求的材料研究衍射仪是多功能的，可以被威奇托州立大学和堪萨斯州其他大学的其他研究人员用于许多其他应用。有了这个设备，堪萨斯州其他研究人员的研究能力将得到极大的提高。此外，学生将接受使用x射线衍射技术的培训，并将在研究生和本科生阶段使用该设备进行研究。%%%***

9803093ChaudhuriThis award provides partial support for instrumentation for the high resolution x-ray characterization of defects and strain in group III nitride based wide band gap semiconductors. A high resolution triple axis materials research diffractometer capable of measuring x-ray rocking curves as well as reciprocal space maps will be acquired. In this unit a triple axis adding a triple-bounce channel-cut Ge(220) analyzer crystal turns the double axis diffractometer into a triple axis diffractometer which gives it a high resolution. Using this diffractometer the interplanar spacing variation due to the strain can be separated from the tilt caused by defects like dislocations. Thus the diffraction peak of a thin film even with a large number of dislocations would be sharp at a certain scanning mode (w - 20 scanning mode) and the peak position can be measured accurately. This will give more precise information on lattice parameters, structure and strain of materials than a double crystal diffractometer. In addition one can obtain the reciprocal space map of the substrate and film separately which gives information on the strain and defects simultaneously. These findings with a high resolution are essential in developing new smaller dimension wide band gap semiconducting materials with less defects and strain and improved opto-electronic properties. The material systems to be studied are used in optical and electronic devices. The structure, strain, composition, defects and polarity in these materials will be analyzed using a comprehensive x-ray diffraction technique which consists of the x-ray high resolution diffractometry and x-ray topographic techniques. These parameters are important because optoelectronic properties and device performance are strongly dependent on them. The experimental values will be compared with the theoretical ones and models will be developed to explain the strain and defects. Specific recommendations will be given to the crystal growers based on these models and improved device fabrication will be realized. Thus a significant contribution can be made in the field of nitride based wide band gap semiconductor devices. This research will be done in collaboration with Kansas State University, Manhattan, KS and other places.This diffractometer will also be made available to other researchers at Wichita State University and at other universities in the state of Kansas. At present there are no high resolution triple axis diffractometers in the state of Kansas. Materials research has been identified as one of the strategic techniques in the state of Kansas. The materials research diffractometer requested is versatile and can be used for many other applications by other researchers in Wichita State University and other universities in Kansas. The research capabilities of other researchers in Kansas will be improved profoundly with this equipment. In addition, students will be trained in the use of x-ray diffraction technique and will be involved in research by using this equipment both at the graduate and undergraduate levels.%%%***