Phonon Polariton Based Infrared Optoelectronics

长波长红外光的检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。具体而言，长波长红外相机可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自然地发射该波长范围内的光。这些探测器还用于探测大气中化学成分的变化，因为我们希望探测的许多不同化学物质都具有这一波长范围内的光谱特征。然而，开发在长波长下工作的半导体探测器和相机一直是一个重大的技术挑战。长波长光与低能量光子相关联，其被窄能隙半导体检测到。这些半导体易受噪声影响，需要低温冷却器才能有效工作，这使得相应的光电探测器昂贵且体积庞大。这项研究将开发与光学天线集成的探测器，以提高探测器捕获的光量。天线将利用晶体的自然振动，即表面声子极化激元，它提供了一种非常有效地将光捕获到探测器的方法。该研究的目的是实现在更高温度下工作的具有改进的噪声性能的探测器，这将增加红外技术在许多应用中的可扩展性。该计划还将通过青年科学与人文研讨会和爱荷华州大学博物馆使爱荷华州的农村社区参与半导体纳米技术。本研究的技术目标是证明表面声子极化激元可以利用来实现8μm波长及更长波长的高效红外探测器。基于声子极化激元的天线的独特性质可以提供比先前在红外探测器中使用的更传统的金属天线显著的优势。声子极化激元模式具有显著减少的材料损耗，并且固有地在红外中产生强的光-物质相互作用以增强检测。此外，由于它们利用未掺杂晶体的性质，它们也不会将扩散的金属颗粒或掺杂剂引入检测器吸收体中。本研究主要包括三个目标：（1）研究砷化镓中声子极化激元与子带间跃迁的共振耦合。这个目标将设计，生长和测量表面声子极化激元增强光电二极管设计共振增强吸收和光电探测。(2)利用外延氧化物中的声子极化激元扩展到其他红外光电探测波长。这个目标将耦合表面声子极化激元模式支持的氧化物生长在量子阱光电二极管，以利用这些材料的声子能量。 (3)使用范德华材料到半导体有源区上的机械转移用于声子极化激元增强。在这一目标中，我们将解决2D材料集成的挑战，以证明在广泛的波长范围内增强检测。除了对红外探测器的直接影响外，该研究还将促进对半导体材料中声子极化激元的理解，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。

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.