Epitaxy and Characterization of h-BN/AlGaN Nanowire Heterostructures: Towards High Efficiency Light Emitters in the Ultraviolet-C Band

非技术性描述：该项目涉及新一代纳米结构宽带隙半导体材料的开发，该材料具有在深紫外光谱中实现高效发光的潜力。如果成功开发，这种材料有望成为新的半导体光源，有可能取代传统的汞灯和准分子激光器，用于广泛的应用，包括水净化，传感和消毒。例如，用高效固态紫外线灯取代汞灯，将消除汞向空气、土壤和水中的排放，并大大减少水处理和处理的电力消耗。更广泛的影响还包括拟议研究的高度跨学科性质，以及对本科生，代表性不足的少数民族和K-12的推广。学生将在高度协作和跨学科的环境中接受培训，包括材料设计和理论（物理学和材料科学），纳米材料生长/合成（材料科学和电气工程）和表征（材料科学和工程）。还将通过表征研讨会以及开发和分发用于离线处理电子显微镜数据的最先进的开源软件工具来加强学生培训和教学。技术说明：该项目的首要目标是研究六方氮化硼（h-BN）和氮化铝镓（AlGaN）纳米线异质结，以实现在传统宽带隙材料难以实现的深紫外波长范围内的有效电流注入和发光。在这个项目中，h-BN/AlGaN纳米线异质结生长的等离子体辅助分子束外延，并使用广泛的技术，包括透射电子显微镜，扫描透射电子显微镜，光致发光光谱，显微拉曼光谱和X射线衍射的特点。由于有效的表面应变弛豫，纳米线的使用可以显著减少与h-BN和AlGaN之间以及与下面的衬底之间的晶格失配相关的位错的形成。更具体地说，该研究旨在通过利用浅受体样硼空位形成来证明h-BN的强p型导电性，并实现h-BN/AlGaN异质结，其中p型h-BN可以用作深紫外透明的导电电极。这可以使得能够替换当前紫外光发射器中的常规电阻性和高吸收性Ga（Al）N接触层，并且因此承诺具有显著增强的效率的紫外光发射器。这项工作是基于两个研究小组之间的密切互动，互补的专业知识，确保材料设计和建模，外延，材料表征，制造和测试之间的闭环。这种跨学科、高度协作的方法也为研究生和本科生提供了一个全面的培训环境。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

Nontechnical description: This project is related to the development of a new generation of nanostructured wide bandgap semiconductor materials, which have the potential to enable efficient light emission in deep ultraviolet spectrum. If successfully developed, such materials promise new semiconductor light sources that can potentially replace conventional mercury lamps and excimer lasers for a broad range of applications, including water purification, sensing, and sterilization. For example, the replacement of mercury lamps by high efficiency solid-state ultraviolet lamps will eliminate mercury emissions to air, soil, and water and also significantly reduce electricity consumption for water processing and treatment. The broader impacts also include the highly interdisciplinary nature of the proposed research and the outreach to undergraduate, underrepresented minorities, and K-12. Students will be trained in a highly collaborative and interdisciplinary environment that includes materials design and theory (physics and materials science), nanomaterials growth/synthesis (materials science and electrical engineering), and characterization (materials science and engineering). Enhanced student training and teaching will also be achieved through characterization workshops and by developing and distributing state-of-the-art, open source software tool for offline processing electron microscopy data. Technical description: The overarching goal of this project is to investigate hexagonal boron nitride (h-BN) and aluminum gallium nitride (AlGaN) nanowire heterojunctions to enable efficient current injection and light emission in the deep ultraviolet wavelength range that was difficult to achieve in conventional wide bandgap materials. In this project, h-BN/AlGaN nanowire heterostuctures are grown by plasma-assisted molecular beam epitaxy and are characterized using a broad range of techniques, including transmission electron microscopy, scanning transmission electron microscopy, photoluminescence spectroscopy, micro-Raman spectroscopy, and X-ray diffraction. Due to the efficient surface strain relaxation, the use of nanowires can significantly reduce the formation of dislocations related to the lattice mismatch between h-BN and AlGaN and with the underlying substrate. More specifically, the research aims to demonstrate strong p-type conductivity of h-BN by exploiting the shallow acceptor-like boron vacancy formation, and realize h-BN/AlGaN heterojunctions wherein the p-type h-BN can function as deep ultraviolet transparent, conductive electrode. This could enable the replacement of conventional resistive and highly absorptive Ga(Al)N contact layers in current ultraviolet light emitters, and therefore promises ultraviolet light emitters with significantly enhanced efficiency. The effort is based on close interaction between two research groups with complementary expertise ensuring a closed loop between materials design and modeling, epitaxy, materials characterization, fabrication, and testing. Such an interdisciplinary, highly collaborative approach also provides a comprehensive training environment for both graduate and undergraduate students.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.