HgCdTe Infrared Focal Plane Arrays For Imaging Spectrometer Applications

HgCdTe focal plane arrays (FPA) have been fabricated for use in an Imaging Spectrometer instrument developed by the Jet Propulsion Laboratory for NASA. Imaging Spectrometer, developed for earth remote sensing applications, provides simultaneous imaging in 100 or more spectral bands. This is achieved by placing an area FPA at the focus of a spectrom-eter. The resultant instrument performs as a pushbroom imager with one axis of the focal plane corresponding to spatial information, and the other axis to spectral information. FPA requirements for current imaging spectrometer designs are discussed. A backside-illuminated hybrid FPA architecture which uses HgCdTe photovoltaic detectors interfaced to a Si CCD multiplexer is presented. HgCdTe material is grown by liquid phase epitaxy on CdTe. The detectors are planar, ion implanted junctions on 68 micron centers. 32 x 32 FPAs have been fabricated from this material for use in the 1 - 4.5 micron and in the 1 - 2.4 micron (short wavelength infrared or SWIR) spectral regions. Complete electro-optical characterization has been done in conditions expected in actual operation. The SWIR FPAs have been evaluated at temperatures of 120 - 150K in backgrounds of 1 x 1012 ph/cm2-s to 5 x 1013 ph/cm2-s. Peak quantum efficiency of the arrays is near 70% with excellent uniformity. Broadband spectral response to 1 micron has been achieved by proper epitaxial layer thickness on these backside-illuminated devices. Near background limited performance has been achieved for over 98% of the detectors.