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At the U.S. Army Research Laboratory, a new ternary semiconductor system CdSexTe1-x,/Si(211) is being investigated as an alternative substrate to bulk-grown CdZnTe substrates for HgCdTe growth by molecular beam epitaxy. Long-wavelength (LW) photovoltaic devices fabricated on this compliant substrate material show diffusion limited performance at 78 K, indicating a high-quality material. The measured R0A at 78 K on Â¿co = 10 Â¿m material is on the order of 340 Â¿ Â· cm2. In addition to single devices, we have fabricated 256 Ã 256 2-D arrays with a 40-Â¿m pixel pitch on LW-HgCdTe grown on CdSexTe1-x/Si(211) compliant substrates. The data show an excellent quantum efficiency operability of 99% at 78 K under a tactical background flux of 6.7 Ã 1015 ph/cm2s. The most probable dark current at peak distribution is 5.5 Ã 109 e-/s and is very consistent with the measured R0A values from single devices. This work demonstrates that CdSexTe1-x/Si(211) substrates provide a potential roadmap for more affordable robust third-generation focal plane arrays.