Nitride Quantum Wells and Photonic Structures - Growth, Optical Studies, and Applications

该项目涉及几个相互关联的研究领域：1)优化III-氮化物材料质量；n型和p型掺杂，特别是对于Al含量相对较高(x 0.5)的AlGaN三元合金和InAlGaN四元合金；以及减少位错和线缺陷。当采用亚微米条侧向外延生长时，台面边缘的过量应变可能占主导地位，导致窗口区域上方的位错较少。还将探索GaN/InAlGaN晶格匹配的四元量子阱(QWS)作为有源介质用于性能改善的紫外光发射器的潜力。2)制备和加工III-氮化物波长尺度的光子结构和器件。将研究电子束光刻图案化和等离子体干法刻蚀来制造波长尺度的光子结构和器件。III-氮化物的独特性质使其对光的产生、引导和开关非常有吸引力，人们将探索将III-氮化物光子元件(如谐振器、光波导、发射器、探测器等)集成到单个芯片上的新结构，为实现基于III-氮化物的集成光子电路奠定基础，以实现广泛的应用。3)深紫外光时间分辨纳米光学研究。一个专门设计的深紫外皮秒时间分辨纳米光谱学系统将用于探测光学性质[光致发光(PL)、电致发光(EL)等]。半导体材料和光子器件的时间分辨率为几个ps，空间分辨率为50 nm，波长范围从红外到深紫外光(到195 nm)。该系统集成了深紫外飞秒激光光谱系统和深紫外近场扫描光学显微镜(NSOM)/AFM系统。它将被用于探测氮化物材料和量子线中的载流子动力学、光学跃迁以及缺陷性质，特别是在AlGaN合金、GaN/AlGaN和GaN/InAlGaN高Al含量(x0.5)的量子线中。其目的是获得控制光学和光电性质的新的认识和方法。还将研究波长尺度发射器和波导中的发射和光传输特性，以便为改进的集成光子器件设计提供输入。该项目致力于具有高度技术相关性的电子/光子材料科学的专题领域的基础研究问题。该项目的一个重要特点是高度重视教育，并将研究与教育相结合。通过直接参与研究，学生将在先进半导体材料、纳米制造技术、半导体物理、半导体材料制造和使用最先进的外延生长、光刻图形、等离子蚀刻和先进材料表征的器件加工领域获得独特的学习和发现机会。该项目还包括与产业界发展战略联盟，进一步加强博士后、研究生和本科生的教育和培训机会。

This project pursues several interconnected research areas: 1) Optimizing III-nitride material quality; n- and p-type doping, particularly for AlGaN ternary alloys and InAlGaN quaternary al-loys with relatively high Al contents (x 0.5); and reduction of dislocations and line defects. When submicron-strip lateral epitaxial overgrowth is employed, relaxation of excess strain at the mesa edges may dominate, resulting in fewer dislocations above the window region. The poten-tial of lattice-matched quaternary quantum wells (QWs) of GaN/InAlGaN as active media for UV emitters with improved performance will also be explored. 2) Fabricating and processing III-nitride wavelength-scale photonic structures and devices. E-beam lithography patterning and plasma dry etching to create wavelength-scale photonic structures and devices will be studied. Unique properties of III-nitrides make them very attractive for the generation, guiding, and switching of light, and new architectures for integrating III-nitride photonic components (e.g., resonators, waveguides, emitters, detectors, etc) onto single chips will be explored to lay the foundation for achieving integrated photonic circuits based on III-nitrides for a wide range of ap-plications. 3) Deep UV time-resolved nano-optical studies. A specially designed deep UV pico-second time-resolved nano-optical spectroscopy system will be used for probing optical proper-ties [photoluminescence (PL), electro-luminescence (EL), etc.] of semiconductor materials and photonic devices with time-resolution of a few ps, spatial resolution of 50 nm, and wavelength range spanning from IR to deep UV (to 195 nm). This system integrates a deep UV femtosecond laser spectroscopy system with a deep UV near-field-scanning-optical-microscopy (NSOM)/AFM system. It will be utilized to probe carrier dynamics, optical transitions, as well as defect properties in nitride materials and QWs, especially in AlGaN alloys, GaN/AlGaN and GaN/InAlGaN QWs with high Al content (x0.5). The aim is to gain new understanding and methods of controlling optical and optoelectronic properties. The emission and light propagation properties in wavelength-scale emitters and waveguides will also be investigated to provide input for improved integrated photonic device design. %%% The project addresses fundamental research issues in a topical area of electronic/photonic materi-als science having high technological relevance. An important feature of the project is the strong emphasis on education, and the integration of research and education. Through direct involve-ment in research, students will have unique learning and discovery opportunities in the areas of advanced semiconductor materials, nano-fabrication techniques, semiconductor physics, semi-conductor materials fabrication and device processing using state-of-the-art epitaxial growth, lithographic patterning, plasma etching, and advanced materials characterization. The project also encompasses development of strategic alliances with industry, which further enhances edu-cation and training opportunities for postdoctorals, graduate, and undergraduate students.***