Epitaxial growth for solar-blind AlGaN photodetector imaging arrays by metalorganic chemical vapor deposition

Solar-blind imaging arrays based on AlGaN p-i-n structures are of high interest for defense applications. We have studied the material issues involved in development of such imaging arrays and have developed discrete photodetector devices with a high external quantum efficiency (EQE) and imaging arrays of high operability. For the discrete devices, a record EQE of 58.1% peaking at 274 nm under zero volt bias was obtained without using an anti-reflecting, (AR) coating. The EQE was seen to have a slight voltage dependence: going up to 64.5% at -5V reverse bias. The responsivity had a drop-off by one order of magnitude for a wavelength change of 4 nm on both the shorter and longer wavelength side. The material quality and uniformity was found to be very good leading to the development of 256 x 256 arrays. A high yield along with uniform, high EQE was obtained for the detector devices in the array leading to a high operability of 99.8%.