In the modern-day FPA, the signal current, together with various other current sources, is integrated on a capacitor in the output node of the amplifier that is located typically within each unit cell. These other current sources include detector dark current, background flux current, and 1/f current. Optimum FPA performance is achieved when the noise is limited primarily by the integrated charge from the background photon flux. This noise is “shot-like” in nature, in that it has essentially a flat noise spectrum across its entire spectral bandwidth out to a frequency given by Df ¼ 1/2tint, where tint is the time dedicated to integrating charge. 1/f noise in FPAs can take one of two forms, namely, (1) systemic 1/f noise or (2) isolated defect 1/f noise. Optimum performance mandates that noise due to integrated dark currents and 1/f currents be much less than background flux noise. In this chapter we will consider the physical sources of shot noise and 1/f noise in IR semiconductor structures.
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