CAREER: Extreme band engineering in polarization graded nanowire heterostructures for high efficiency photonics

技术：该项目将通过实验室研究和教育推广，促进学术界和公众对用于光子学的光学/电子材料原理的理解。宽带隙iii -氮化物半导体跨越紫外-可见-近红外光谱，在紫外-可见光源和探测器中寻找节能应用。自组装氮化物纳米线由于对晶格失配的高容忍度而增加了异质结构的设计灵活性。该项目将在纳米线异质结构中实现新型光学和电学功能，以实现先进的高效光子学。总体而言，GaN、AlN和InN中的极化电荷和带隙不能维持在单一异质结构中，而不会由于应变松弛而产生大量的位错。纳米线避开了外延应变的限制，使梯度AlGaN和InGaN异质结构中电子和空穴的极端能量景观成为可能，同时保持单晶无缺陷的活性区。由于极化电荷能够以高速和高效率分离电子和空穴，使得高速光电探测器能够覆盖广泛的能量范围，因此异质结构阵列可能表现出巨大的内置电场。偏振分级也将用于实现纳米线中无杂质p和n型掺杂，从而避免了纳米结构中杂质掺杂的问题，并将用于演示无掺杂的pn结LED。为了实现这些异质结构，将研究任意选择纳米线直径和密度的自组装GaN和InN纳米线在Si（111）上的分子束外延生长的生长相图的系统映射，并采用一系列结构，光学和电子技术，包括SEM， z -对比TEM， XRD，时间分辨光致发光，电致发光，纳米线传输，陷阱光谱学用于研究纳米线结构和极化电荷/掺杂现象的基本输运和光学性质。非技术：控制原子结合形成纳米级半导体晶体的方式，可以有效地将光转换为电，反之亦然。然而，即使是有科学倾向的学生和教师，在很大程度上也不知道太阳能转换、照明和显示技术的基础，完全不知道晶体生长的科学。为了解决这一不足，俄亥俄州立大学将把针对高中生的教程和实验室演示整合到广泛的推广基础设施中，包括针对少数民族学生和女性的开放日和夏令营。材料科学与工程系将举办一系列为期一天的夏令营活动，包括电光能量转换材料的实践教程/实验室演示。同样的教程将通过COSI科学博物馆的电子专家计划远程传送给全国各地的高中生，该计划还将提供教程开发和评估的框架。

Technical: This project will advance the academic and public understanding of the principles of optical/electronic materials used for photonics through laboratory research and educational outreach. Wide bandgap III-Nitride semiconductors span the ultraviolet-visible-near infrared spectrum finding energy efficient applications in ultraviolet-visible light sources and detectors. Self-assembled Nitride nanowires increase the design flexibility in heterostructures due to high tolerance to lattice mismatch. This project will achieve new types of optical and electrical functionality in nanowire heterostructures for advanced high efficiency photonics. In bulk, polarization charge and bandgaps in GaN, AlN, and InN cannot be maintained in a single heterostructure without generating large numbers of dislocations due to strain relaxation. Nanowires sidestep the constraint of epitaxial strain making possible extreme energy landscapes for electrons and holes in graded AlGaN and InGaN heterostructures, while maintaining single crystal defect-free active regions. A remarkable array of heterostructures are possible exhibiting large built-in electric fields due to polarization charge that separate electrons and holes with high speed and efficiency, properties that enable high speed photodetectors covering a broad range in energy. Polarization grading will also be used to achieve impurity free p and n type doping in nanowires, which sidesteps the problem of impurity doping in nanostructures, and will be used to demonstrate a dopant-free pn-junction LED. To achieve these heterostructures, a systematic mapping of the growth phase diagram of molecular beam epitaxy growth of self-assembled GaN and InN nanowires on Si (111) for arbitrary selection of nanowire diameter and density will be investigated, and a suite of structural, optical, and electronic techniques will be employed, including SEM, Z-contrast TEM, XRD, time-resolved photoluminescence, electroluminescence, nanowire transport, and trap spectroscopy to examine fundamental transport and optical properties as they relate to nanowire structure and polarization charge/doping phenomena.NonTechnical: Controlling how atoms combine to form nanoscale crystals of semiconductors allows efficient conversion of light to electricity, and vice versa. However, even scientifically inclined students and teachers are largely unaware of the foundations of remarkable solar conversion, lighting, and display technologies, and completely unaware of the science of crystal growth. To address this shortfall, tutorials and lab demonstrations geared toward high school students will be integrated into the extensive outreach infrastructure at Ohio State, including open houses and summer camps that target minority students and women. A series of day long and summer camp events in the department of Materials Science and Engineering will take part in a hands-on tutorial/lab demonstration on materials for electro-optical energy conversion. The same tutorial will be remotely beamed to high school students around the country through the Electronics Experts program at the COSI science museum, which also provides a framework for tutorial development, and evaluation.