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Diffusion current is a current in a semiconductor ... one can observe that when a zero voltage is applied to the semi-conductor diode, the drift current totally ...
The Shockley equation is a constant current (steady state) relationship, and thus doesn't account for the diode's transient response, which includes the influence of its internal junction and diffusion capacitance and reverse recovery time.
In a p-n junction diode, electrons and holes are the minority charge carriers in the p-region and the n-region, respectively. In an unbiased junction, due to the diffusion of charge carriers, the diffusion current, which flows from the p to n region, is exactly balanced by the equal and opposite drift current. [1]
The amount of minority diffusion in the near-neutral zones determines the amount of current that can flow through the diode. Only majority carriers (electrons in n-type material or holes in p-type) can flow through a semiconductor for a macroscopic length.
The Shockley diode equation relates the diode current of a p-n junction diode to the diode voltage .This relationship is the diode I-V characteristic: = (), where is the saturation current or scale current of the diode (the magnitude of the current that flows for negative in excess of a few , typically 10 −12 A).
This diffusion current is governed by Fick's law: = where: F is flux. D e is the diffusion coefficient or diffusivity; is the concentration gradient of electrons; The diffusion coefficient for a charge carrier is related to its mobility by the Einstein relation.
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