Description: We propose to advance the Ga-free InAs/InAsSb type II superlattice (T2SL) materials technology for very long wavelength infrared (VLWIR) focal plane arrays (FPAs) by passivating lifetime-limiting defects with hydrogen from inductively coupled plasma (ICP) H2-plasmas. In Phase II, 1k x 1k detector arrays will be fabricated and hybridized to matching read-out integrated circuits for implementation in future Earth and Planetary science infrared imaging instruments and become part of future space missions. Larger format FPAs (2k x 2k) will be realized as part of follow-up developments extending beyond Phase II. In Phase I, we will compute and optimize the electronic band structures, optical properties, Auger coefficients and ideal diffusion-limited dark currents of InAs/InAsSb T2SL absorber materials. The operating temperatures and overall thickness will be used as part of a trade-off study designed to achieve the quantum efficiency and dark current program goals. Shockley-Read-Hall minority carrier lifetimes of T2SLs are predicted to increase due to hydrogen-passivation, leading to larger signal-to-noise ratios for improved range of detection, enhanced discrimination capabilities, or operation at higher temperatures. Reducing the electrical activity of defects by passivating them with hydrogen is equivalent to lowering their density, and has proven successful in other semiconductor systems. The proposed hydrogenation technique makes use of the same dry-etch equipment employed during FPA manufacturing, making it easy to implement. In addition to the potential to remove the deleterious effects of bulk material defects, ICP hydrogenation also improves the detector's surface passivation quality. Smaller pixels, reduced integration times, and systems with larger fields-of-view will be realized, allowing the imaging of fast changing scenes over long ranges.

Benefits: Large format VLWIR FPAs will be a valuable asset for a variety of Earth, planetary and astrophysics science experiments that require infrared imaging. The fabrication of large format VLWIR FPAs with high quantum efficiency, broad spectral response extending to 14 microns, and low noise will greatly increase the imaging capability of Discovery 13/14, New Frontiers 4, Europa Jupiter System, Mars 2018 and other space exploration missions. These detectors can also be used on Earth-based systems, such as in NASA?s Aqua satellite for meteorological infrared weather tracking of storm systems, the hyperspectral infrared imager (HYSPIRI), or the climate absolute radiance and refractivity observatory (CLARREO). Another potential application of the proposed technology is the Triangulation and LIDAR Automated Rendezvous and Docking (TriDAR) system that integrates a thermal imager used by NASA for real-time guidance during rendezvous and docking of the International Space Station.

Single detector and small arrays sensitive to VLWIR radiation have a wide range of commercial applications, such as spectrometry, thermometry, high‐end industrial manufacturing, and hotspot detection. Low cost arrays with lightweight characteristics will meet various requirements in meteorology, geophysics, geology, law enforcement, remote environmental sensing, search and rescue, and emergency response including firefighting. If operating temperatures can be enhanced, the product would also have applications in medical systems, commercial airlines, and ground transportation.