Phonon Polariton Based Infrared Optoelectronics

University Of Iowa, Iowa City IA

Investigators

Abstract

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.