High efficiency photon detection is a critical component for many NASA missions, including both earth monitoring instruments and exoplanet exploration. Improved photon detectors provide increased sensitivity, higher resolution, and enable reduced size and weight. For earth sensing, Ultraviolet (UV) wavelengths provide a unique capability to monitor ozone, chlorine compounds, bromine compounds, and aerosols. For astrophysics, UV provides a critical window for the determination of the atmosphere of exoplanets. Recently, solid state imagers have been developed with the capability to provide high spatial resolution imaging with single photon sensitivity using various silicon approaches (Quantum Image Sensors, single photon avalanche diodes, scientific CMOS, etc.) These sensors often provide single photon sensitivity, high quantum efficiency, and good imaging performance. However, these sensors are limited by certain properties of silicon, including high thermal noise rates and high sensitivity to background radiation. To improve UV performance, we proposed to develop single photon avalanche diodes (SPADs) and single photon avalanche diode arrays using AlGaN materials, providing larger photosensitive areas with improved sensitivity, lower thermal noise, and excellent rejection of background radiation (solar blind).
Potential NASA applications include a broad range of UV instruments, including spectrometers and hyperspectral imagers. UV instruments are used in earth observation satellites, particularly those developed to measure atmospheric ozone, chlorine, or benzene. Space based telescopes can also benefit from UV photon detectors and photodetector arrays, including straightforward UV spectroscopy of the universe as well as exoplanet discovery instruments, where UV spectroscopy can be used to determine the atmospheric constituents of exoplanets.
The annual market for ultrasensitive photodetectors is estimated to be in excess of $1B. Solid-state alternatives to UV photomultipliers can enable improved spatial resolution and higher quantum efficiency, enabling applications ranging from remote sensing, to intercontinental missile launch detection, to high efficiency detection of gamma ray detectors using scintillators (DOE and NIH).