Chapter 8 - HgCdTe 2D arrays-technology and performance limits

Abstract

The aim of this chapter is to explain the underlying technology and performance limits of 2D focal plane arrays and then describe how manufacturers have approached the challenge. There are many possible technologies for producing 2D focal plane arrays in HgCdTe and there is a tendency for different manufacturing centers to adopt their own unique processes. The evolution of 2D focal plane arrays has depended on matching the spatial resolution and cost of existing systems. The chapter also describes the work being conducted in many centers to develop very low cost technology and cameras with a low cost of ownership. HgCdTe continues to be developed as the material of choice for high performance long wavelength arrays and has an established market at the medium and short wavelength ranges. The most important market for HgCdTe 2D arrays is in thermal imaging in the medium waveband. HgCdTe arrays have competition from lead salt detectors, indium antimonide (InSb) and metal silicide Schottky detectors in the medium wave (MW) band and multiple quantum well detectors in the long wave (LW). HgCdTe has a strong optical absorption coefficient and only thin layers are needed to produce high quantum efficiency. Important applications in the short wave (SW) waveband include: thermal imaging (using nightglow), spectroscopy and active imaging using lasers. The definition of a GEN III detector can differ between different nations but the general guideline is any detector that offers an imaging advantage over conventional first- and second-generation systems. The ultimate performance potential of HgCdTe will ensure that it is the material of choice for all high-performance infrared systems. The chapter concludes with a description of the research and development paths that centers throughout the world are using to advance towards so-called GEN III detectors.