Electrically Injected Ultraviolet AlGaN Photonic Nanocrystal Surface Emitting Lasers

该项目涉及在中紫外光谱中工作的表面发射半导体激光器的示范，这将使许多革命性的应用成为可能，从在集成电路生产中取代笨重和有毒的受激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，还没有在中紫外和深紫外光谱中工作的表面发射激光二极管的证明，这受到常规氮化铝镓（AlGaN）材料的广泛缺陷和位错、基于AlGaN的分布式布拉格反射器（DBR）的不良电流传导和低反射率的存在的限制。因此，目前的中紫外线和深紫外线光源是基于汞灯和氙灯，它们耗电量大、体积大、价格昂贵，而且经常含有有毒物质。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的表面发射激光二极管，可以有效地在紫外光谱中工作。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，这可能是唯一可能的替代技术，以取代传统的准分子激光器和汞灯用于水净化和消毒。该项目提供了机会，教育学生在广泛的主题，从纳米材料，光子学，纳米技术，光电子学。拟议研究的高度跨学科性质还允许研究人员提供研究和培训机会，通过各种计划活动，让本科生，代表性不足的少数民族和K-12参与。在这个项目中，研究人员建议开发全半导体，电注入，低阈值表面发射激光二极管在UV-B波段（280-315 nm）工作。表面发射激光将通过利用无位错的氮化铝镓（AlGaN）光子纳米晶体的二维谐振模式来实现，而不是使用传统的电阻和位错AlGaN分布式布拉格反射器（DBR）。此外，通过利用无缺陷AlGaN纳米晶体中镁（Mg）受体杂质带的形成，将实现先前在宽带隙氮化铝（AlN）和富Al AlGaN中不可能实现的有效p型导电。（Al）GaN dot-in-chip异质结构将被生长和表征，这将克服与非辐射表面复合相关的挑战，以及宽带隙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UV激光器。详细了解激光器的性能，包括阈值，壁插效率，近场和远场分布，稳定性和可靠性将被执行。该项目的成功将为开发在紫外光谱下工作的低阈值表面发射激光二极管开辟一个新的范例，其中器件性能不再受到缺乏高质量DBR、大晶格失配和衬底可用性的限制。该奖项反映了NSF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.