Exploiting Novel Device Structures for Deep Ultraviolet Emitters

摘要标题：开发用于深紫外发射器的新型器件结构芯片级深紫外（DUV）光源的开发是广泛应用所必需的，例如探测蛋白质中的固有荧光、医疗设备/人员去污和生物降解。发光二极管（LED）在250 nm附近工作的外量子效率（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。 DUV发射器的EQE的重大进展将需要利用破坏性设备概念。本计画的目的是探索利用新的p型层策略来克服富铝镓氮中p型导电率低的问题。拟议的努力不仅将在具有改进EQE的DUV发光二极管（LED）制造方法上取得突破，而且还将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/设备设计和使用最先进的实验设施加工领域进行培训。该项目将为初级研究人员提供参加会议和研讨会的机会，并接触DUV光子器件的真实的世界应用。教育活动还将包括通过高级设计项目和所需的项目实验室课程将本科生融入研究。 外联活动包括让PI担任着名的克拉克学者的导师，为来自全国各地的极具天赋的高中生带来对科学和技术的欣赏，并增加科学和工程的多样性。所提出的DUV发射极层结构基于六方氮化硼（hBN）和AlGaN异质结构带隙和掺杂工程。通过在氮化物DUV发射器中实施直接宽带隙和高导电hBN p型层策略，电子阻挡层和p型接触层的p型导电率和DUV透明度将显著增加。这将显著改善自由空穴注入和EQE，降低工作电压和发热，并增加器件工作寿命。 通过MOCVD生长的原位掺杂将建立对外延h-BN膜的p型电阻率和导电类型的控制。DUV发射极结构，包括p型hBN将生长在蓝宝石厚AlN模板，以减少位错密度。欧姆接触处理，包括退火条件将被优化。深紫外发光二极管将被制造，其I-V，L-I特性，和墙壁插头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.