Dear friends, as we know that, semiconductor materials as a beautiful property i.e np= ni^2
here n and p respectively denotes electron and hole densities in the extrinsic semiconductor. The quantity ni represents the densities in intrinsic semiconductor and and is therefor independent of of the doping level.
Why can we not say that n+p should remain constant?.
Dear Dr. Shiromani,
In a semiconductor, the product of hole and electron concentrations always remains constant at a given temperature. Doping has the effect of modifying only the ratio of the concentrations but not their product. Consequently, if the ratio of the concentrations is modified, their sum n+p should be modified too.
a) This relation is only valid in equilibrium (e.g. no illumination, currents, etc.)
b) Even from a mathematical point of view, if x*y = const. it's easy to show that (x+y) shouldn't be constant
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