Multicolor UV Seeker Based on GaN/GaAs Heterostructures

APA Optics will develop a monolithic UV seeker for use in flame sensing and passive or tactical threat warning systems. The key to the technical approach is the deposition of high optical/electrical quality Al(x)Ga(1-x)N over GaAs substrates and using it to fabricate back to back Schottky barrier detectors. Al(x)Ga(1-x)N is a compound III/V semiconductor system with a bandgap tunable from 220 to 365 nanometers (x=1 to x=0). Thus selecting x=0.4 we expect our UV sensors to detect only the UV emission from the flame (or plume) and not respond to the IR signal. This makes the sensor immune to false signals from the hot furnace background or the missile body. We also plan to use the GaAs substrate to monolithically integrate the preamplifier with the UV sensor. Our sensor approach is unique because we can also use the substrate to integrate an IR sensor on the same chip. This opens up interesting possibilities of target and flame type discrimination.