Exploiting Novel Device Structures for Deep Ultraviolet Emitters

芯片级深紫外（DUV）光源的发展是广泛应用的需要，如探测蛋白质中的固有荧光，医疗设备/人员净化和光催化。发光二极管（led）在250 nm附近的外部量子效率（EQE）仍然很低（低于3%）。目前，AlGaN半导体是DUV光源的默认选择。富铝AlGaN合金的p型导电性差是限制这些器件EQE的主要障碍。在DUV发射器的EQE方面取得重大进展将需要利用破坏性设备概念。本项目旨在探索利用新的p型层策略来克服富al AlGaN中p型电导率低的内在问题的DUV器件结构。所提出的努力不仅会在制造具有改进EQE的DUV发光二极管（led）的方法上取得突破，而且还会导致用于一系列应用的新型光子材料和器件的技术进步。通过参与研究，学生将在纳米制造技术，材料/器件设计和使用最先进的实验设备加工等领域接受培训。该项目将为初级研究人员提供参加会议和研讨会的机会，并获得接触DUV光子器件的实际应用的机会。教育活动还将包括通过高级设计项目和必要的项目实验课程将本科生纳入研究。拓展活动包括让pi担任著名的克拉克学者的导师，为来自全国各地的高天赋高中生带来科学和技术的欣赏，并增加科学和工程的多样性。提出的DUV发射极层结构是基于六方氮化硼（hBN）和AlGaN异质结构带隙和掺杂工程。通过在氮化DUV发射体中实施直接宽禁带高导电性的hBN p型层策略，可以显著提高电子阻挡层和p型接触层的p型电导率和DUV透明度。这将显著提高自由孔注入和EQE，降低工作电压和热量产生，并延长器件的使用寿命。通过原位掺杂和MOCVD生长，可以控制外延h-BN薄膜的p型电阻率和导电性。结合p型hBN的DUV发射极结构将生长在具有厚AlN模板的蓝宝石上，以降低位错密度。欧姆触点加工包括退火条件将得到优化。将制造DUV led，其I-V， L-I特性和壁插效率将与器件结构和制造工艺相关。

Abstract Title: Exploiting Novel Device Structures for Deep Ultraviolet Emitters Development of chip-scale deep ultraviolet (DUV) light sources is required for a wide range of applications such as probing intrinsic fluorescence in a protein, medical equipment/personnel decontamination, and photocatalysis. The external quantum efficiency (EQE) of Light Emitting Diodes (LEDs) operating in the region around 250 nm is still quite low (below 3%). Currently, AlGaN semiconductors are default choice for the DUV light sources. The poor p-type conductivity of Al-rich AlGaN alloys is the major obstacle that limits the EQE of these devices. Significant advances in the EQE of DUV emitters will require the exploitation of disruptive device concepts. This project aims to explore DUV device structures that exploiting new p-type layer strategies to overcome the intrinsic problem of low p-type conductivity in Al-rich AlGaN. The proposed efforts would not only yield breakthroughs in methods for the fabrication of DUV light emitting diodes (LEDs) with improved EQE, but would also lead to technological advancements in novel photonic materials and devices for a range of applications. Through the involvement in the research, students will be trained in the areas of nano-fabrication techniques, material/device design and processing using the state-of-the-art experimental facilities. The project will provide junior researchers with opportunities to participate in conferences and workshops, and gain exposure to the real world applications of DUV photonic devices. Educational activities will also include the integration of undergraduates into research via senior design projects and required project lab courses. Outreach activities include having the PIs serve as mentors of the prestigious Clark Scholars to bring an appreciation of science and technology to highly gifted high school students from around the nation and to increase diversity in science and engineering. The proposed DUV emitter layer structure is based on hexagonal boron-nitride (hBN) and AlGaN heterostructure bandgap and doping engineering. By implementing the direct wide bandgap and highly conductive hBN p-type layer strategy in nitride DUV emitters, p-type conductivities and DUV transparency of the electron blocking layer and p-type contact layer will be dramatically increased. This will significantly improve the free hole injection and EQE, reduce the operating voltage and heat generation, and increase the device operating lifetime. Control over the p-type electrical resistivity and conductivity type of epitaxial h-BN films will be established by in-situ doping via MOCVD growth. DUV emitter structures incorporating p-type hBN will be grown on sapphire with thick AlN templates to reduce the dislocation density. Ohmic contacts processing including annealing conditions will be optimized. DUV LEDs will be fabricated and their I-V, L-I characteristics, and wall plug efficiency will be correlated with the device structures and fabrication processes.