NASA's interest in UV photodetectors includes spectroscopic analysis for planetary and atmospheric studies; temperature and composition analysis of young stars; and composition, density and temperature measurements of the interstellar medium. These missions require UV detectors and detector arrays with high sensitivity, low noise, fast response time and high spectral selectivity. Since these observations are frequently made from platforms operating above Earth's atmosphere (which absorbs UV), the photodetectors must also be small size, low mass, low power, and low cost to make the best use of limited payloads and NASA resources. Extended operation in space also requires the devices to be radiation resistance, temperature resistance, highly reliable and have long lifetime. Photodetectors are used in a wide range of applications for commercial, industrial, scientific and military markets. Photodetectors based on wide bandgap semiconductor materials operate in the ultraviolet (UV) spectral range. UV photodetectors can be used in spectroscopy, optical communications and optical data storage. Because of their large bandgap, these detectors are blind to visible and solar radiation. Visible/solar blind UV photodetectors are useful for monitoring and detection of high temperature heat sources in ambient light, such as for flame detectors or for detecting the exhaust signatures of hostile aircraft and missiles.