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

非技术描述：该项目与新一代纳米结构宽带隙半导体材料的开发有关，这种材料具有在深紫外光光谱中实现高效光发射的潜力。如果开发成功，这些材料有望开发出新的半导体光源，有望在包括净水、传感和杀菌在内的广泛应用中取代传统的汞灯和准分子激光器。例如，用高效固态紫外线灯取代汞灯将消除对空气、土壤和水的汞排放，并显著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，以及面向本科生、代表性不足的少数群体和K-12。学生将在高度协作和跨学科的环境中接受培训，其中包括材料设计和理论(物理和材料科学)、纳米材料生长/合成(材料科学和电气工程)以及表征(材料科学和工程)。还将通过举办表征讲习班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放源码软件工具来加强学生培训和教学。技术描述：该项目的主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，以便在深紫外光波长范围内实现有效的电流注入和发光，这在传统的宽带隙材料中是难以实现的。本项目采用等离子体辅助分子束外延技术生长了h-BN/AlGaN纳米线异质结，并用透射电子显微镜、扫描电子显微镜、光致发光光谱、显微拉曼光谱和X射线衍射等技术对其进行了表征。由于有效的表面应变弛豫，纳米线的使用可以显著减少由于h-BN和AlGaN之间以及与衬底之间的晶格失配而导致的位错的形成。更具体地说，该研究旨在通过利用浅受主类空位的形成来证明h-BN具有很强的p型导电性，并实现h-BN/AlGaN异质结，其中p型h-BN可以作为深紫外光透明的导电电极。这使得能够取代现有紫外光发射器中传统的阻性和高吸收的Ga(Al)N接触层，从而有望显著提高紫外光发射器的效率。这项工作基于两个拥有互补专业知识的研究小组之间的密切互动，以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优势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.