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

技术支持：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族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找到节能应用。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的光学和电学功能，用于先进的高效光子学。在体中，GaN、AlN和InN中的极化电荷和带隙不能保持在单个异质结构中，而不会由于应变弛豫而产生大量位错。纳米线避开了外延应变的限制，使渐变AlGaN和InGaN异质结构中的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有源区。由于极化电荷，异质结构的显着阵列可能表现出大的内置电场，其以高速度和效率分离电子和空穴，使得高速光电探测器能够覆盖宽范围的能量。偏振分级也将用于实现纳米线中的无杂质p型和n型掺杂，这回避了纳米结构中杂质掺杂的问题，并将用于演示无掺杂剂pn结LED。为了实现这些异质结构，将研究在Si（111）上分子束外延生长自组装GaN和InN纳米线的生长相图的系统映射，以任意选择纳米线直径和密度，并将采用一系列结构、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、纳米线输运、和陷阱光谱学，以检查基本的传输和光学性质，因为它们与纳米线结构和极化电荷/掺杂现象有关。非技术性：控制原子如何结合联合收割机形成纳米级半导体晶体，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也基本上不知道显着的太阳能转换，照明和显示技术的基础，并且完全不知道晶体生长的科学。为了解决这一不足，面向高中生的教程和实验室演示将被纳入俄亥俄州广泛的外展基础设施，包括面向少数民族学生和妇女的开放日和夏令营。材料科学与工程系的一系列为期一天的夏令营活动将参加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，该计划还为教程开发和评估提供了一个框架。

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.