Investigating the structural properties of nitride-based semiconductors in the scanning electron microscope

在扫描电子显微镜中研究氮化物基半导体的结构特性

• 批准号: 2278012
• 金额: --
• 依托单位: University of Strathclyde
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2019
• 资助国家: 英国
• 起止时间: 2019 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2278012
• 关键词: Investigating; structural; properties; nitride; based

Nitride thin films exhibiting high structural quality are crucial for optimising the performance of next generation nitride semiconductor-based devices. These include AlGaN-based ultraviolet (UV) light emitting diodes (LEDs) which can be used for a wide range of applications including sterilisation and treatment of skin disease; AlGaN-based high mobility electron transistors which will facilitate the production of compact power supplies, microwave transmitters and electric cars; and InGaN-based green lasers which can be used in compact projectors and laser displays. The production of high structural quality thin films requires the understanding and reduction/elimination of structural defects such as grain boundaries, threading dislocations and stacking faults, which limit device performance, e.g., lead to the generation of heat rather than light in LEDs, induce electrical shorts and limit device lifetime.In this PhD project Dale will apply the scanning electron microscope (SEM) techniques of electron backscatter diffraction (EBSD) and electron channelling contrast imaging (ECCI) to both understand and optimise the nanostructure of materials produced by our collaborators from both academia and industry from across the world. He will both characterise materials and advance the applications of the ECCI and EBSD techniques through engagement in the development and application of new advanced SEMs and data analysis software.ECCI micrographs may be produced when a sample is placed so that a plane or planes are at, or close to, the Bragg angle with respect to the incident electron beam. Any deviation in crystallographic orientation or in lattice constant due to local strain, will produce a variation in contrast in the resultant ECCI micrograph. Extremely small changes in orientation and strain are detectable, revealing, for example, low angle tilt and rotation boundaries and atomic steps and enabling extended defects such as dislocations and stacking faults to be imaged.In EBSD the sample is tilted at around 70 degrees to the normal of the incident electron beam. The impinging electrons are scattered through high angles forming a diverging source of electrons which can be diffracted. The resultant electron backscatter diffraction pattern (EBSP) consists of a large number of overlapping bands, known as Kikuchi bands, which are closely related to a 2-D projection of the crystal structure. Changes in crystal orientation for example, can be mapped by acquiring EBSPs from a mesh of points on a sample. EBSD is a well-established technique for texture analysis and for quantifying grain boundaries and crystal phases.The introduction of cross-correlation based analysis of EBSPs has also made possible measurements of relative strain, lattice tilts and twists and crystal polarity.Strathclyde researchers have pioneered the application and combination of these techniques for the characterisation of nitride thin films and are presently collaborating with both academic and industrial researchers to support the development of novel nitride materials. Present collaborators include: Prof. Peter Parbrook, Tyndall National Institute, University College Cork, Ireland; Prof. Michael Kneissl, TU Berlin, Berlin, Germany; Dr Sylvia Hagedorn, Ferdinand-Braun-Institut, Berlin, Germany; Prof. Ferdinand Scholz, Ulm University, Ulm, Germany; Dr Philippe Vennéguès, CRHEA-CNRS, Valbonne, France; Prof. Tao Wang, University of Sheffield, UK; Dr Philip Shields, University of Bath, UK; Prof. David Wallis, Universities of Cardiff and Cambridge, UK; IQE Europe Ltd; and OSRAM Opto Semiconductors, Regensburg, Germany.We are also collaborating with Dr Ken Mingard at NPL; Dr Philippe Vennéguès, CRHEA-CNRS, Valbonne, France; TESCAN, France and Prof Aimo Winkelmann at Laser Zentrum Hannover e.V., Hannover, Germany on the development of the EBSD and ECCI techniques.

具有高结构质量的氮化物薄膜对于优化下一代氮化物半导体器件的性能至关重要。其中包括基于 AlGaN 的紫外线 (UV) 发光二极管 (LED)，其可用于多种应用，包括消毒和皮肤病治疗；基于AlGaN的高迁移率电子晶体管将促进紧凑型电源、微波发射器和电动汽车的生产；以及基于 InGaN 的绿色激光器，可用于紧凑型投影仪和激光显示器。高结构质量薄膜的生产需要了解和减少/消除结构缺陷，例如晶界、螺纹位错和堆垛层错，这些缺陷限制了器件性能，例如导致 LED 中产生热量而不是光、引起电气短路并限制器件寿命。在这个博士项目中，Dale 将应用电子背散射衍射 (EBSD) 和扫描电子显微镜 (SEM) 技术。 电子通道对比成像 (ECCI)，用于了解和优化我们来自世界各地学术界和工业界的合作者生产的材料的纳米结构。他将通过参与新的先进 SEM 和数据分析软件的开发和应用来表征材料并推进 ECCI 和 EBSD 技术的应用。当放置样品以使一个或多个平面相对于入射电子束处于或接近布拉格角时，可以生成 ECCI 显微照片。由于局部应变而导致的晶体取向或晶格常数的任何偏差都会在最终的 ECCI 显微照片中产生对比度的变化。方向和应变的极小变化是可以检测到的，例如揭示小角度倾斜和旋转边界以及原子台阶，并能够对位错和堆垛层错等扩展缺陷进行成像。在 EBSD 中，样品与入射电子束的法线倾斜约 70 度。撞击的电子通过高角度散射，形成可衍射的发散电子源。由此产生的电子背散射衍射图案 (EBSP) 由大量重叠带（称为菊池带）组成，它们与晶体结构的二维投影密切相关。例如，晶体取向的变化可以通过从样品上的点网格获取 EBSP 来绘制。 EBSD 是一种成熟的织构分析以及量化晶界和晶相的技术。基于互相关的 EBSP 分析的引入还使得相对应变、晶格倾斜和扭曲以及晶体极性的测量成为可能。斯特拉斯克莱德研究人员率先应用和组合这些技术来表征氮化物薄膜，目前正在与学术界和工业界合作 研究人员支持新型氮化物材料的开发。目前的合作者包括：爱尔兰科克大学廷德尔国家研究所的 Peter Parbrook 教授； Michael Kneissl 教授，柏林工业大学，德国柏林； Sylvia Hgedorn 博士，费迪南德-布劳恩研究所，柏林，德国； Ferdinand Scholz 教授，乌尔姆大学，德国乌尔姆； Philippe Vennéguès 博士，CRHEA-CNRS，法国瓦尔博讷；王涛教授，英国谢菲尔德大学； Philip Shields 博士，英国巴斯大学； David Wallis 教授，英国卡迪夫大学和剑桥大学； IQE 欧洲有限公司；我们还与 NPL 的 Ken Mingard 博士合作； Philippe Vennéguès 博士，CRHEA-CNRS，法国瓦尔博讷；法国 TESCAN 和德国汉诺威 Laser Zentrum Hannover e.V. 的 Aimo Winkelmann 教授致力于 EBSD 和 ECCI 技术的开发。