Focal Plane Arrays

doi:10.1117/3.2536930.ch5

Focal Plane Arrays

Book: Narrow-Gap Semiconductor Photodiodes

Author(s): Antoni Rogalski, Krzysztof Adamiec, Jaroslaw Rutkowski

Published: 2000

https://doi.org/10.1117/3.2536930.ch5

Author Affiliations +

Abstract

During the 1950s and 1960s IR detectors were built using single-element cooled lead salt detectors primarily for anti-air missile seekers. At the same time, rapid advances were being made in narrow-gap semiconductors that would later prove useful in extending wavelength capabilities and improving sensitivity. These developments paved the way for the highly successful forward-looking IR (FLIR) airborne systems developed in the 1970s. In 1970, Boyle and Smith published a paper reporting the charge-coupling principle which is a simple, extremely powerful concept based upon the transfer of charge packets in a MIS structure. In the area of IR technique, the use of charge transfer devices (CTD) holds the key to substantial improvements in thermal imaging. CTD arrays offer significant advantages for focal plane applications. There is a large research activity directed toward two-dimensional (2D) “staring” array detectors consisting of more than 106 elements. The thermal detectors that are relative newcomers are narrowing the gap with photon detectors with respect to numbers of detectors per chip. IR FPAs have nominally the same growth rate as dynamic random access memory (RAM) ICs (which have had a doubling rate of approximately 18 months) but lag behind in size by about 5–10 years. ROICs are somewhat analogous to dynamic RAM—only readouts require a minimum of three transistors per pixel compared to one per memory cell. Readouts are also analogous with an emphasis on low noise inputs and generally maximum charge storage capacity.