480 x 2 hybrid HgCdTe infrared focal plane arrays

Abstract

To meet the sensitivity and resolution requirements of high-performance long-wavelength infrared (LWIR) imaging systems, we developed hybrid HgCdTe 480 X 2 infrared focal plane arrays (IRFPAs) for the 8 - 10 micrometers band. We connected the hybrids using indium bumps and a sapphire wiring substrate to reduce the thermal expansion mismatch between the silicon readout circuits and the photodiode arrays. Using the mature liquid phase epitaxy (LPE) technology and a CdZnTe substrate, we fabricated LWIR photodiode arrays. Each photodiode array consists of 240 X 2-element n+/n/p diodes formed by boron implantation. The arrays have an average zero-bias resistance of 3.8 M(Omega) and a shunt resistance of more than 100 M(Omega) for a 10.5 micrometers cutoff wavelength. For the readout devices, we used n-channel charge coupled devices (CCDs) with charge capacities greater than 4 X 10<SUP>7</SUP> electrons, and 4 signal outputs capable of 6 MHz data rates. The input stages of the CCD include skimming and partitioning functions. Operating at 80 K, the arrays had a mean laboratory D*<SUB>(lambda</SUB> p) of 6.4 X 10<SUP>10</SUP> cmHz<SUP>0.5</SUP>/W with f/1.2 optics. The detectivity variation ((sigma) /m) was 14%, and the operable pixel yield exceeded 99%.