High-Density Schottky Barrier IRCCD Sensors For Remote Sensing Applications

A palladium silicide (Pd2Si) Schottky barrier sensor for satellite push-broom multispectral imaging in the 1-3.5 μm short wavelength infrared (SWIR) is being developed. The SWIR sensor will utilize Schottky barrier infrared charge-coupled device (IRCCD) technology to realize dual-band integrated circuits with two linear arrays of 512 detectors each. The monolithic, two-color devices will have 30-μm center-to-center detector spacing and an 80 to 90% fill-factor. These integrated circuits will be suitable for chip-to-chip abutment, thus providing the capability to produce large, multiple-chip focal planes with contiguous, in-line detectors. To date, monolithic 32-x-64 and 64-x-128 palladium silicide interline transfer IRCCDs have been developed. These silicon imagers exhibit a low response nonuniformity of typically 0.2 to 1.6% rms. Spectral response measurements of Pd2Si p-type Si devices yield quantum efficiencies of 7.9% at 1.25 μm, 5.6% at 1.65 μm, and 2.2% at 2.22 μm. Improvement in quantum efficiency is expected by optimizing the different structural parameters of the Pd2Si detectors. The dark current level of Pd2Si detectors permits radiometric operation at 120-125K with a measured dark current of 2 nA/cm2 (120K). This operating temperature is complemented by a low power dissipation of 18 μW per detector for nominal operation of a push-broom 2-x-512 device. These operational parameters will permit the realization of satellite-borne, passively cooled, dual-band focal planes with thousands of detector elements. It has been shown that the performance of the technology will permit the dual-band sensor to meet the noise-equivalent-delta reflectivity (NEAp) requirements for accurate classification of earth resources features.