High-Performance Long-Wavelength Infrared HgCdTe Focal Plane Arrays Fabricated on CdSeTe Compliant Si Substrates

At the U.S. Army Research Laboratory, a new ternary semiconductor system CdSe_xTe_1-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 ¿_co = 10 ¿m material is on the order of 340 ¿ · cm². In addition to single devices, we have fabricated 256 × 256 2-D arrays with a 40-¿m pixel pitch on LW-HgCdTe grown on CdSe_xTe_1-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 × 10¹⁵ ph/cm²s. The most probable dark current at peak distribution is 5.5 × 10⁹ e-/s and is very consistent with the measured R₀A values from single devices. This work demonstrates that CdSe_xTe_1-x/Si(211) substrates provide a potential roadmap for more affordable robust third-generation focal plane arrays.