Phonon Polariton Based Infrared Optoelectronics

对长波红外线的探测可以帮助我们监测环境和工程过程，这些过程是气候变化等社会挑战的一部分。具体地说，长波红外相机可以用于温度变化的非接触式成像，因为所有接近室温的材料都会在这个波长范围内自然发射光线。这些探测器还用于检测大气中化学成分的变化，因为我们希望检测的许多不同的化学物质在这个波长范围内都有光谱特征。然而，开发工作在长波长的半导体探测器和相机一直是一个重大的技术挑战。长波长光与窄能隙半导体探测到的低能光子有关。这些半导体对噪音很敏感，需要低温冷却器才能有效运行，这使得相应的光电探测器既昂贵又笨重。这项研究将开发与光学天线集成的探测器，以增强探测器捕获的光量。天线将使用晶体的自然振动，即所谓的表面声子极化子，它提供了一种非常有效地将光捕获到探测器的方法。这项研究的目标是实现在更高温度下工作的具有更高噪声性能的探测器，这将增加红外技术在许多应用中的可扩展性。该计划还将通过初级科学和人文研讨会以及爱荷华大学博物馆，让爱荷华州的农村社区利用半导体纳米技术。这项研究的技术目标是证明可以利用表面声子极化子来实现8μm波长和更长波长的高效红外探测器。基于声子极化的天线的独特性质可以提供比以前用于红外探测器的更传统的金属天线更大的优势。声子极化模显着减少了材料损失，并在红外中固有地产生强烈的光-物质相互作用，以增强探测。此外，由于它们利用了非掺杂晶体的特性，它们也不会将扩散的金属颗粒或掺杂剂引入探测器吸收体。这项研究包括三个关键目标：(1)展示砷化镓中声子极化子与红外探测中的子带间跃迁的共振耦合。这一目标将设计、生长和测量表面声子极化增强型光电二极管，旨在共振地增强吸收和光检测。(2)利用外延氧化物中的声子极化子扩展到其他红外探测波长。这一目标将耦合表面声子极化模由生长在量子阱光电二极管上的氧化物支持，以利用这些材料的声子能量。(3)利用Van-der-Waals材料在半导体有源区的机械转移来增强声子极化。在这个目标中，我们将解决2D材料集成的挑战，以展示在广泛波长范围内的增强检测。除了红外探测器的直接影响外，拟议的研究还将促进对半导体材料背景下的声子极化子的理解，并在此过程中开发新的材料组合和结构。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The detection of long wavelength infrared light can help us monitor environmental and engineering processes which are part of societal challenges such as climate change. Specifically, long wavelength infrared cameras can be used for non-contact imaging of temperature changes, as all materials near room temperature naturally emit light within this wavelength range. These detectors are also used for detecting changes in chemical composition in the atmosphere, as many different chemicals we wish to detect possess a spectral signature in this wavelength range. However, developing semiconductor detectors and cameras that operate at long wavelengths has been a major technological challenge. The long wavelength light is associated with low energy photons, which are detected by narrow energy gap semiconductors. These semiconductors are susceptible to noise and require cryogenic coolers to operate efficiently, making corresponding photodetectors expensive and bulky. This research will develop detectors integrated with optical antennas, which enhance the amount of light captured by the detector. The antennas will use the natural vibrations of crystals, known as surface phonon polaritons, which offer a means to trap light extremely efficiently to the detector. The objective of the research is to realize detectors with improved noise performance operating at higher temperatures, which will increase the scalability of infrared technologies for many applications. This program will also be to engage rural communities in Iowa with semiconductor nanotechnologies through the Junior Science and Humanities symposium, and at the University of Iowa museums.The technical objective of this research is to demonstrate that the surface phonon polaritons can be leveraged to realize highly efficient infrared detectors at 8μm wavelengths and longer. The unique properties of phonon polariton based antennas could offer a significant advantage over more conventional metallic antennas which have been used in infrared detectors previously. Phonon polariton modes have significantly reduced material losses and inherently produce strong light-matter interactions in the infrared for enhancing detection. Further, as they leverage the properties of undoped crystals, they also do not introduce diffused metal particles or dopants into the detector absorber. The research consists of three key objectives (1) Demonstrate resonant coupling of phonon polaritons in gallium arsenide to intersubband transitions for infrared detection. This objective will design, grow, and measure surface phonon polariton enhanced photodiodes designed to resonantly enhance absorption and photodetection. (2) Utilize phonon polaritons in epitaxial oxides for expansion to other infrared photodetection wavelengths. This objective will couple surface phonon polariton modes supported by oxides grown on a quantum well photodiode to leverage the phonon energies of these materials. (3) Use mechanical transfer of Van-der-Waals materials onto semiconductor active regions for phonon polariton enhancement. In this objective we will address the challenges of 2D material integration to demonstrate enhanced detection at a wide range of wavelengths. In addition to the immediate impact in infrared detectors, the research proposed will also advance understanding of phonon polaritons in the context of semiconductor materials and develop new material combinations and structures in the process.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.