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The use of silicon as a substrate alternative to bulk CdZnTe for epitaxial growth of HgCdTe for infrared (IR) detector applications is attractive because of potential cost savings as a result of the large available sizes and the relatively low cost of silicon substrates. However, the potential benefits of silicon as a substrate have been difficult to realize because of the technical challenges of growing low defect density HgCdTe on silicon where the lattice mismatch is ϳ19%. This is especially true for LWIR HgCdTe detectors where the performance can be limited by the high (ϳ5 ϫ 10 6 cm Ϫ2 ) dislocation density typically found in HgCdTe grown on silicon. We have fabricated a series of long wavelength infrared (LWIR) HgCdTe diodes and several LWIR focal plane arrays (FPAs) with HgCdTe grown on silicon substrates using MBE grown CdTe and CdSeTe buffer layers. The detector arrays were fabricated using Rockwell Scientific's planar diode architecture. The diode and FPA and results at 78 K will be discussed in terms of the high dislocation density (ϳ5 ϫ 10 6 cm 2 ) typically measured when HgCdTe is grown on silicon substrates.

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A comparison of photovoltaic HgCdTe/A1203, HgCdTe/CdZnTe, InGaAs/lnP and photoconductive GaAs/A1GaAs quantum well infrared photodetector (QWIP) detector technologies has been conducted at Rockwell by exploiting the ability to selectively hybridize disparate mosaic detector arrays to an assortment of silicon multiplexers. Hybrid FPA characteristics are reported as functions of operating temperature from 32.5K to room temperature and at photon backgrounds from 1 06 to mid-1016 photons/cm2-sec. The staring arrays range in size from about sixteen thousand to over a million pixels. Background-limited detectivities significantly exceeding 1014 cm4iEIW were achieved.