The proposed work aims to demonstrate significant improvement in AlGaN-based detectors and detector arrays by employing single crystal AlN substrates, which practically eliminates leakage induced by screw dislocations. By employing defect controlled APDs on single crystal AlN, we aim to demonstrate sensitivity over the whole UVC range (120 - 275 nm) while being solar and visible blind. We will provide APDs and their arrays of varying pixel resolution and pixel size capable of Geiger mode operation and photon counting. The detectors will be capable of elevated temperature operation allowing for extreme environment operations in places such as Venus. In addition, we also aim to demonstrate low dark currents at high linear gains by point defect control. We aim to demonstrate AlGaN-based photon counters with low dark counts and sensitivity only in the UVC range (< 275 nm) with solar and visible spectrum rejection, quantum efficiency exceeding 70%, high multiplication gain exceeding E6, and low dark current. During Phase I we will demonstrate Geiger mode operation and photon counting with >TRL 3. In a possible Phase II, we will extend our efforts and will have achieved TRL 6. Anticipated Benefits Development of solar blind UV APDs will enable various technologies that advance space exploration and observation. Venus exploration missions such as VERITAS and DAVINCI require spectrophotometers in the UV spectral range that are capable of withstanding the extreme environment of the planet. AlGaN based photodetectors would enable long-term operation with higher reliability in a hot and corrosive environment while exhibiting lower voltages, lower volume and lower weight and excellent solar spectrum rejection. A potential commercial application of the developed photon counters is bio-chem detection systems based on compact Raman spectroscopy. Real-time, on-site, ultra-sensitive detection of harmful bio and chemical agents requires a solar blind UV photon counter. Raman spectroscopy in the proposed 240-260 nm range is needed to avoid potential fluorescence of specimen.
