Generalized photonic IR detector

Based on the previous consideration, one can divide physical methods for photodetector performance improvement into two general groups. One of them are optical or equilibrium methods, and the other are nonequilibrium methods. 

We denote as optical or equilibrium methods all various procedures that increase the number of photons of the useful signal within the detector active area. This means that they improve the performance of photonic MWIR or LWIR detectors without causing a nonequilibrium between charge carriers and the semiconductor crystal lattice. 

Nonequilibrium methods are those that change the carrier distribution by elevating the effective temperature of carriers over the crystal lattice temperamre. Thus, obtained nonequilibrium causes spatial redistribution of charge carriers, and can be thus utilized to decrease the carrier concentration in the desired part (the active area) of a photonic detector. This decreases carrier concentration-dependent g-r process rates, causes thermally-induced noise drop and as a result produce effects similar to those of cryogenic cooling. 

The equilibrium methods can be used for photodetectors generally, while nonequilibrium methods are convenient for different types of semiconductor photonic detectors. Mutual for both equilibrium and nonequilibrium methods is that they can be implemented utilizing different micro and nanofabrication methods. 

The presented four main parts of a detector may be or may not be separate units. Actually, both their structures and their functions may overlap. For instance, the blocks (a) and (b) indirectly decrease noise by decreasing the active area volume. The block (b) also directly decreases noise since it increases reabsorption. 

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