An Indium Gallium Arsenide Visible/SWIR Focal Plane Array for Low Light Level Imaging

PIN photodiodes fabricated from indium gallium arsenide lattice-matched to indium phosphide substrates In.53Ga.47AsInP exhibit low reverse saturation current densities JD 10exp -8 Asq cm, and high shunt resistance-area products RoA 10exp 6 omega-sq cm at T290K. Backside-illuminated, hybrid-integrated InGaAs FPAs are sensitive from 0.9 micrometers to 1.7 micrometers. 290K detectivities, D, greater than 10exp 14 cm-square root of HzW are demonstrated. This represents the highest room temperature detectivity of any infrared material. The long wavelength cutoff 1.7 micrometers makes In.53Ga.47As an idea match to the available airglow that has major peaks at 1.3 micrometers and 1.6 micrometers. The short wavelength cut-on at 0.9 micrometers is due to absorption in the InP substrate. We will report on new InGaAs FPA epitaxial structures and processing techniques. These have resulted in improved performance in the form of a 10 x increase in detectivity and visible response via removal of the InP substrate. The resulting device features visible and SWIR response with greater than 15 quantum efficiency at 0.5 micrometers while maintaining the long wavelength cutoff. Imaging has been demonstrated under overcast starlighturban glow conditions with cooling provided by a single stage thermoelectric cooler. Details on the material structure and device fabrication, quantitative characterization of spectral response and detectivity, as well as examples of night vision imagery are presented.