ABL (Airborne Laser) Detection Sensor Improvements

MDA is developing deployable airborne systems such as the Airborne Laser (ABL) for boost-phase missile defense. The ABL’s mission would significantly benefit from enhanced target detection and ranging capabilities. We propose an active sensing system compatible with ABL that is based on HgCdTe avalanche photodiodes (APDs), which are an attractive choice for active sensing applications because their internal gain mechanism can improve signal to noise ratios. Moreover, they offer an advantageous combination of several factors, including high quantum efficiencies and high frequency response. We propose to design and fabricate long wavelength infrared (LWIR) APD focal plane arrays based on HgCdTe. As a novel approach, we propose a lateral current collection device design that will have larger optical detection areas than electrical junction areas, and also have the advantages of reduced dark currents and relatively high resistances compared to traditional planar heterostructures. In the Phase I effort, we will use Taurus-Medici, a 2-dimensional device modeling tool, to design and simulate single element HgCdTe LWIR lateral current collection APDs, grow the structures by molecular beam epitaxy, fabricate single element detectors with lithography, inductively coupled plasma etching and metal evaporation, and characterize the electrical and optical performance of the active sensing detectors.