Noise in Nonequilibrium Magnetoconcentration Photodetectors

The calculated photoelectric gain of a magnetoconcentration photoconductor increases with the material composition approaching the optimum at a given tem-peramre and tends to unity, except near the surface with high recombination rate. 

Spatial distribution of g-r noise current through a magnetoconcentration detector is shown in Fig. 3.57 for an operating temperamre of T = 220 K and a magnetic induction of 2 T. 

Noise current slowly decreases with the position within the photoconductor, reaches a minimum and then sharply increases toward the back surface (with high recombination velocity.) After reaching its maximum, it becomes lower again because of a sharp drop of photoelectric gain, in spite of the fact that the g-r processes are actually largest just in that position. 

The dependence of calculated total noise current through a magnetoconcentration photoconductor on applied bias is shown in Fig. 3.58 for various operating temperatures. To see only the influence of transport parameters to the behavior of the detector, the material composition was kept constant at x = 0.186 for all cases shown in Fig. 3.58, although this means a deviation of the device characteristics from the optimum value (responsivity and specific detectivity are obtain for different X at each particular temperature.) 

58 Noise current versus bias for HgCdTe magnetoconcentration photodetector at different temperatures 

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