HgCdTe hybrid focal plane

Abstract Second-generation IR systems, consisting of 2-D mosaics of IR detectors, have been under intense development for the last few years. One of the most successful architectures has been a HgCdTe hybrid focal plane array (FPA), using a Si charge-coupled device (CCD) readout chip interfaced to epitaxial HgCdTe. Detection is made by backside-illuminated photovoltaic detectors with high fill factors and quantum efficiency. The detectors are coupled into the CCD by In bumps which mass bond each detector in the mosaic to a CCD input. Advances have been made in uniform, large area HgCdTe detector material that can be grown with a bandgap from less than 0.1 eV to greater than 1 eV. CCD architectures have been developed with simple, linear inputs and dynamic ranges up to 80 dB. Hybrid FPAs are currently being tested in prototype imaging systems, for detecting thermal differences as well as reflected sunlight in the IR. In the 3–5μm region, these arrays have proven capable of noise-equivalent temperature differences as low as 0.01 K, acquired at a 400 Hz frame rate. In addition to improving current imaging systems, these area arrays allow new system concepts to be brought to fruition.