Large-format MWIR focal plane arrays

Abstract
Medium wavelength IR arrays have been develoepd which have 1024×768 pixels on a 26 micron pitch. The arrays are made from epitaxially grown indium antimonide, the use of which confers two advantages over conventional InSb owing to the ability to exercise atomic level control of dopants and material thicknesses. Firstly, the photodiodes can be grown on degenerately doped InSb substrates which have a high degree of transparency, so the requirement for the substrate to be thinned is much reduce dleading to simplified manufacture. Secondly, it offers the potential for an increase in operating temperature of many tens of degrees, through elimination of contact leakage currents, though we focus on 80K performance here for comparison with conventional structures. We present initail results form arrays which indicate high operability, despite the need to stitch reticles in the fabrication of the silicon read-out circuit, and temperature sensitivity close to the theoretical limit. Imaging from the arrays compares very favorably with that taken using generation II cameras and gives confidence that this technology offers a cost effective route to large format MWIR systems.

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