Electrically Injected Ultraviolet AlGaN Photonic Nanocrystal Surface Emitting Lasers

该项目涉及在中紫外（UV）光谱下工作的表面发射半导体激光器的演示，这将实现许多革命性的应用，从取代集成电路生产中的笨重和有毒准分子激光器到超高密度光存储，再到高分辨率光谱分析和生物医学诊断。迄今为止，由于传统氮化铝镓（AlGaN）材料存在广泛的缺陷和位错，电流传导不良，以及基于AlGaN的分布式Bragg反射器（DBRs）的低反射率，还没有在中深紫外光谱中工作的表面发射激光二极管的证明。因此，目前的中深紫外光源是基于汞灯和氙灯，这是耗电，体积庞大，价格昂贵，往往含有有毒物质。在这个项目中，通过利用氮化铝镓纳米结构，研究人员将解决这些基本挑战，并将设计和开发新一代表面发射激光二极管，可以在紫外光谱中有效地工作。该项目的成功将为实现高效固态紫外光源开辟一个新的范例，这可能是唯一可能取代传统准分子激光和汞灯进行水净化和消毒的替代技术。该项目为学生提供了广泛的主题教育机会，包括纳米材料、光子学、纳米技术和光电子学。拟议研究的高度跨学科性质也允许研究者通过各种计划活动提供涉及本科生，代表性不足的少数民族和K-12的研究和培训机会。在这个项目中，研究者建议开发全半导体、电注入、低阈值表面发射激光二极管，工作在UV-B波段（280-315 nm）。利用无位错的氮化铝镓（AlGaN）光子纳米晶体的二维共振模式来实现表面发射激光，而不是使用传统的电阻性和位错的AlGaN分布布拉格反射器（dbr）。此外，利用无缺陷AlGaN纳米晶体中镁（Mg）受体杂质带的形成，可以实现以前在宽带隙氮化铝（AlN）和富al AlGaN中不可能实现的高效p型传导。（Al）GaN点纳米晶体异质结构将被生长和表征，这将克服与非辐射表面重组相关的挑战，以及宽禁带半导体的大透明载流子密度，从而实现以前不可能实现的低阈值紫外激光器。详细了解激光器的性能，包括阈值、壁塞效率、近场和远场分布、稳定性和可靠性。该项目的成功将为开发在紫外光谱中工作的低阈值表面发射激光二极管开辟新的范例，其中器件性能不再受到缺乏高质量dbr，大晶格不匹配和衬底可用性的限制。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This project is related to the demonstration of surface emitting semiconductor lasers operating in the mid-ultraviolet (UV) spectrum, which will enable many revolutionary applications, ranging from replacing bulky and toxic excimer lasers in the production of integrated circuits to ultra-high-density optical storage to high-resolution spectral analysis and biomedical diagnosis. To date, there have been no demonstration of surface emitting laser diodes operating in the mid and deep UV spectra, which has been limited by the presence of extensive defects and dislocations of conventional aluminum gallium nitride (AlGaN) materials, poor current conduction, and low reflectivity of AlGaN-based distributed Bragg reflectors (DBRs). Consequently, the current mid and deep UV light sources are based on mercury and xenon lamps, which are power hungry, bulky, and expensive and often contain toxic substances. In this project, by utilizing aluminum gallium nitride nanostructures, the researchers will address these fundamental challenges and will design and develop a new generation of surface emitting laser diodes that can operate efficiently in the UV spectrum. Success of this project will open a new paradigm for achieving efficient solid-state UV light sources, which may enable the only likely alternative technology to replace conventional excimer lasers and mercury lamps for water purification and disinfection. This project provides the opportunity to educate students in a broad range of topics, ranging from nanomaterials, photonics, nanotechnology, and optoelectronics. The highly interdisciplinary nature of the proposed research also allows the investigator to provide research and training opportunities to involve undergraduate, underrepresented minorities, and K-12 through various planned activities. In this project, the investigator proposes to develop all-semiconductor based, electrically injected, low threshold surface emitting laser diodes operating in the UV-B band (280-315 nm). Surface emitting lasing will be achieved by exploiting the two-dimensional resonance modes of dislocation-free aluminum gallium nitride (AlGaN) photonic nanocrystals, instead of using conventional resistive and dislocated AlGaN distributed Bragg reflectors (DBRs). Moreover, efficient p-type conduction, that was not previously possible in wide bandgap aluminum nitride (AlN) and Al-rich AlGaN, will be achieved by exploiting the formation of a magnesium (Mg) acceptor impurity band in defect-free AlGaN nanocrystals. (Al)GaN dot-in-nanocrystal heterostructures will be grown and characterized, which will overcome the challenges associated with nonradiative surface recombination, as well as the large transparency carrier density of wide bandgap semiconductors, thereby enabling low threshold UV lasers that were not previously possible. A detailed understanding of the laser performance, including threshold, wall-plug efficiency, near and far-field profile, stability and reliability will be performed. Success of this project will open a new paradigm for developing low threshold surface emitting laser diodes operating in the UV spectrum, wherein the device performance is no longer limited by the lack of high quality DBRs, large lattice mismatch, and substrate availability.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.