Carrier Distribution in Extraction-Exclusion Photodiode

The spatial distribution of carrier concentration in extraction structures was calculated using the general model of nonequiUbrium photodetectors under the influence of purely electrical field (3.65)-(3.69) with the boundary conditions (3.70)-(3.74). The generation term was calculated according to (1.85), (1.86). One of the convenient methods of calculation is to use finite difference method (e.g. [379]). 

The obtained values for the concentrations of both carrier types in the most part of the active area are very close to each other. More significant differences can be noted only at the edges of the region. The electron concentration is slightly below the hole concentration. An increase of reverse bias voltage decreases the concentration of both carrier types below the equilibrium level in the n region (dashed line). 

Calculations for p n stmctures give results almost identical to those for p jtn photodiodes with the same doping levels. The main difference is that here the level of electron concentration is slightly above the hole level. 

According to the analysis of the behavior of extraction devices published in [380, 381] an increase of the active region thickness in an extraction-exclusion detector, independently on the doping level, decreases the depletion of both types of carriers and impedes exclusion and extraction processes, i.e., in both cases there is a maximum thickness of the active region. This Umiting value of thickness is 

3 Charge Carrier Management (Thermal Noise Engineering) 

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