Description: Purpose: In this Phase I SBIR program, a collaboration between Magnolia Optical Technologies and Georgia Institute of Technology, we propose to advance the development of GaN and AlGaN ultraviolet (UV), deep-UV (DUV), and far-UV (FUV) single-photon avalanche detectors (SPADs) using the well-developed Si photomultiplier (SiPM) concept and then, in future SBIR Phases, to commercialize practical devices for NASA system needs, e.g., Large UV/Optical/IR Surveyor (LUVOIR) and many other DoD, DoE, and commercial applications. Our team has collaborated on the development of III-N APDs in the past. Our overall innovation in this SBIR will be to ultimately create the III-N analog of the silicon-based avalanche photodiode (APD) arrays—commonly referred to as silicon photomultipliers (SiPMs): a back-illuminated hybrid III-N SPAD-focal-plane array (FPA) device flip-chip-bonded and electrically coupled to a Si CMOS read-out circuit. Use of Funding: These Phase I funds will be used to grow, process, and test additional GaN-based APDs to further evaluate some of our innovative concepts for improving the overall performance of photon-counting III-N UV SPADs. Markets: Future markets include NASA, DoD, DoE and many "dual-use" and commercial applications. Example applications include PET scanners, UV LIDAR, contamination control, early missile threat detection and interception, chemical and biological threat detection, UV flame monitoring, and UV environmental monitoring. The global commercial UV sensor market is projected to grow substantially over the next five years. The market growth is powered by commercial and defense applications that will transition to our UV-SPAD devices that can directly benefit from the performance capabilities and features of the III-N UV-SPAD detector technology.

Benefits: UV photon detectors are widely used by NASA missions, e.g., the ultraviolet spectrograph (UVS) on the Juno Mission, and in the future 2030 UVEX (UltraViolet EXplorer) Mission, and many other future NASA missions. As noted in the Jet Propulsion Laboratory (JPL), Microdevices Laboratory (MDL) webpage, Solar system exploration missions and Earth observation have utilized the ultraviolet spectrum to answer questions about a variety of topics from the origin of Earth to the atmospheres of the other planets, moons, asteroids, and comets in the solar system. Nearly all the spacecraft sent to other planets and solar system objects have carried ultraviolet spectrometers on board with great success. We expect that the NASA programs Explorers, Discovery, Cosmic Origins, Physics of the Cosmos, Solar-Terrestrial Probes, Vision Missions, and Earth Science Decadal Survey missions will all benefit from our technology development. One potential NASA application for III-NPMs is the Large UV/Optical/IR Surveyor (LUVIOR) for the development of a large-format FUV photodetector with high fill-factors and pixel counts that can be assembled into large arrays for application to ECLIPS, HDI, and LUMOS. As noted in the LUVIOR technical note, the high dynamic range, solar-blind characteristics, and the radiation hardness of III-N APDs are other important characteristics for this and similar applications. Another important application area for NASA is monitoring contamination control (CC) for critical future Earth and astrophysical science missions. Another mission area where III-NPMs can play a transformative role is for Sensors and Sensor Systems Targeting Aerosols and Clouds (SBIR Topic S11.05) for studies of autonomous aerosol optical depth (AOD) UV detection in the wavelength range ~340nm is required.Non-NASA applications will initially be for other US government-related critical system needs since the initial costs for these higher-performance SPADs, UV APD photodetector arrays, and systems are going to be higher than for existing older lower-performance "cost depreciated" technologies. Example applications of UV photodetectors currently employing solid-state SiPMs include PET scanners, UV LIDAR, contamination control, early missile threat detection and interception, chemical and biological threat detection, UV flame monitoring, UV environmental monitoring, secure space-to-space communications, pollution monitoring, and water sterilization. Other common uses are for UV photodetectors in instrumentation systems, e.g., a UV detector is very commonly used detector in HPLC analysis and in UV spectrophotometers. Many of these applications require very sensitive devices with high signal-to-noise ratio and high response speed. Currently, a variety of solid-state UV detectors are available, mainly Si-based photodetectors and APD-based photomultipliers (SiPMs). These devices can be very sensitive in the visible-near IR regions with low noise and quick response. However, they have significant limitations for operation in the UV, especially FUV, such as the need for expensive filters to block lower-energy photons (e.g., visible and IR light), their long-term degradation and lower UV efficiency. To avoid these disadvantages, we propose to further develop III-N UV detectors based on wide bandgap semiconductors and develop the III-NPM concept.