Toward AlGaN Focal Plane Arrays for Solar-Blind Ultraviolet Detection

Missile approach warning (MAW) systems of airborne military platforms require ultrasensitive detection capabilities in the solar-blind UV regime below 280 nm. Today, these needs are answered with UV photomultiplier tubes, which are bulky, complex, and require external filtering to suppress clutter signatures beyond 280 nm.This study investigates whether AlGaN focal plane array (FPA) detectors may develop into a viable alternative. The compact, lightweight, all-solid-state solution promises intrinsic solar blindness and excellent out-of-band suppression ratios realizable at affordable costs on large-area substrates. Yet, does today's state of technology allow mastering the fabrication processes so that the electrooptical performance is sufficient to achieve the required sensitivity? Herein, three device wafers are grown by metalorganic chemical vapor deposition and subsequently processed into detector arrays with a spatial resolution of 640 x 512 pixels on a 15 mu m pitch. After hybridization with an off-the-shelf capacitive transimpedance input amplifier (CTIA) read-out integrated circuit (ROIC), their electrooptical performance is characterized. The characterized FPAs show a very low percentage of defective pixels, excellent linearity at high photon fluxes, and, at low flux, their already remarkable sensitivity is limited by the off-the-shelf CTIA ROIC. Therefore, with further improvements MAW systems based on AlGaN FPAs seem feasible.