Advanced materials techniques for large HgCdTe focal plane arrays

The advent of advanced materials techniques (MOCVD and MBE) for growing HgCdTe on alternative substrates has opened new avenues for IR system development. 128×128 and 256×256 SWIR staring arrays of HgCdTe grown on sapphire substrates offer highly sensitive viewing of distant astronomical objects. Similar sized HgCdTe/sapphire MWIR arrays at 77 K have shown in-lab noise equivalent temperature differences <0.02 K and excellent operability and uniformity. LWIR diodes formed by ion-implantation in HgCdTe on either GaAs or Si substrates show performance comparable at 77 K to devices made in HgCdTe grown on more common II-VI substrates. This suggests that substrate producibility limits. The authors discuss the following topics: basic alternative-substrate HgCdTe materials and device architectures for SWIR, MWIR, and LWIR; description of SWIR and MWIR imaging arrays; LWIR results; and implications for future IR FPAs