<title>Advanced multiplexed readouts for T<15K focal plane arrays</title>

Abstract

Rockwell International has developed 128 X 128 element multiplexers and very-long- wavelength infrared (VLWIR), Si:As blocked impurity band (BIB) hybrid focal plane arrays (HFPAs) for both low and high flux applications. The multiplexers are fabricated with an n- well CMOS process with 2 micrometers design rules optimized for the <EQ 14 K operating temperature of Si:As BIB detectors. For low flux applications, the unit cell integration capacitance has been reduced to values as small as 0.133 pF and measures to reduce multiplexer photon emission have been implemented. For the high flux regime, the unit cell charge capacity has been maximized with a direct injection input (for large integrated voltage swing) and by using large in-cell capacitance. Devices with a large number of high speed output lines (16) for high frame rate operation have been developed. High quality (near 100% pixel operability with very small (< 3%) nonuniformity) HFPAs have been repeatedly demonstrated with both types of arrays. An improved cryogenic multiplexer process, with 1.2 micrometers design rules, is being used to design and lay out a 256 X 256 element multiplexer for a BIB HFPA. This array, expected in late 1994, will be optimized for high flux applications and will provide improved capability for ground-based, VLWIR imaging instruments for astronomy and other applications.