This chapter discusses the fundamental limitations to IR photodetector performance imposed by the statistical nature of the generation and recombination processes in the semiconductor material, and radiometric considerations. We will try to establish the ultimate theoretical sensitivity limit that can be expected for a detector operating at a given temperature. The model presented here is applicable to any of the photodetector classes mentioned in Chapter 1. We will also attempt to describe how to improve the performance of the device by taking into account fundamental physics. The nonfundamental limitations, such as Shockley-Read processes, contact phenomena, bias power dissipation, high electric fields, dislocations, fabrication problems, current gain, and quantum efficiency peculiarities, will be addressed later in this chapter.
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