Development of high performance ultraviolet and near-infrared detector technologies

Electro-optical detection in ultraviolet (UV) and near-infrared (NIR) bands has distinct advantages for various applications. UV/NIR wavelengths are desired for a variety of NASA, defense and commercial applications. While UV and NIR detection technologies are governed by similar physical principles, a major differentiating factor lies in the choice of detector materials. Using the GaN/AlGaN material system, we are developing avalanche photodiodes (APDs) as discrete devices with high gains and responsivities. These devices, based on high crystalline quality metal organic chemical vapor deposition (MOCVD) growth on lattice-matched GaN substrates, demonstrate uniform and reliable distribution of breakdown voltage and leakage currents with gains of above 10⁶. For NIR detection we have employed epitaxial layer deposition of germanium on silicon for room temperature operation. This development is focused on demonstrating very low noise performance as a result of low dislocation densities and dark currents. Both these material/device technologies can be adapted to create arrays of detectors for a variety of applications. The primary objective in developing these sensing and imaging technologies is to advance the state-of-the-art to benefit diverse UV/NIR applications for NASA, defense, and commercial applications.