The Bulk-Regions Recombination Current Density

To the assumptions noted in section 7 we must now add an assumption (d) concerning the domination of majority carriers in the bulk regions  

This means that the trap energy level must not be too far from the intrinsic level. For example p/n 1 implies that for x - W/2, 

Under these conditions one finds in the p-type region 

It follows that there exists a minority life time t defined by 

If e is the (small and approximately constant) electric field in the p-type region, the minority current density is 

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