Design and Development of High Gain AlGaN Avalanche Photodiode Arrays

Future NASA earth science systems and missions, specifically those involving high resolution Lidar measurements, will benefit from the development of large-area, high gain AlGaN ultraviolet avalanche photodiodes (UV-APD) arrays operating at room temperature at the 355 nm wavelength. The high quality GaN/AlGaN UV-APD detector arrays are epitaxially grown using an optimized metal organic chemical vapor deposition (MOCVD) technique. The use of lattice-matched bulk GaN substrates provides low dark/leakage current by minimizing defects from the substrate, while alternately AlN substrates can be used to provide backside-illuminated, high fill factor UV-APD devices. In addition to low dark current noise, the solid-state UV-APD devices demonstrate high quantum efficiencies with very high avalanche gains (>10^5). For the Phase II SBIR effort, we shall model, design, develop, and demonstrate the AlGaN UV-APD array technology for implementation in future NASA missions. We will work with NASA for modelling UV-APD arrays for performance improvements in NASA Earth Science systems. Magnolia will collaborate with Prof. Russ Dupuis of Georgia Tech, an expert in III-N material growth and device technology, for MOCVD growth, fabrication, and characterization of the UV-APD array devices. This will entail the enhancement of surface passivation techniques for further performance improvements, developing high quality, low resistivity n- and p-type contacts, as well as incorporating antireflection coatings. It is expected based on measurement data that these devices can perform in Geiger-mode at ~355 nm with high single-photon detection efficiencies for operation in photon-starved environments. Based in part on results attained from the Phase I effort, the AlGaN-based UV-APD technology can meet and/or exceed system requirements in applications such as high resolution Lidar to benefit NASA systems for advancing future missions