INDEPENDENTLY ACCESSED BACK-TO-BACK HGCDTE PHOTODIODES - A NEW DUAL-BAND INFRARED DETECTOR

We report the first data for a new two-color HgCdTe infrared detector for use in large dual-band infrared focal plane arrays (IRFPAs). Refer red to as the independently accessed back-to-back photodiode structure , this novel dual-band HgCdTe detector provides independent electrical access to each of two spatially collocated back-to-back HgCdTe photod iodes so that true simultaneous and independent detection of medium wa velength (MW, 3-5 mu m) and long wavelength (LW, 8-12 mu m) infrared r adiation can be accomplished. This new dual-band detector is directly compatible with standard backside-illuminated bump-interconnected hybr id HgCdTe IRFPA technology. It is capable of high fill factor, and all ows high quantum efficiency and BLIP sensitivity to be realized in bot h the MW and LW photodiodes. We report data that demonstrate experimen tally the key features of this new dual-band detector. These arrays ha ve a unit cell size of 100 x 100 mu m(2), and were fabricated from a f our-layer p-n-N-P HgCdTe film grown in situ by metalorganic chemical v apor deposition on a CdZnTe substrate. At 80K, the MW detector cutoff wavelength is 4.5 mu m and the LW detector cutoff wavelength is 8.0 mu m Spectral crosstalk is less than 3%. Data confirm that the MW and LW photodiodes are electrically and radiometrically independent.