Junction Model and Space-Dependences

As an example of a recombination current density calculation consider the transition region of a p-n junction, fig. 7.1. Band edges and quasi-Fermi levels are 

Then the volume density of electrons and holes in a non-degenerate semiconductor at uniform temperature are 

The concentrations n(x), p(x) can be expressed in terms of n using the fact that 

Thus from point L one sees that the electron concentration in the bulk n-type region has become constant for x W/2 at a value n 

The asymmetry of the doping of the junction is measured by 6 in the sense that 6=0 for a S3nnmetrically doped junction. 

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