Physics Asked by Nanda Sinha on December 6, 2020
Why do the current in diode in forward bias configuration called “Diffusion current” even if this current is a resultant of external voltage supply which create electric field in diode ,hence should be called drift current? I also acknowledge that there is concentration gradient as P side is full of holes and N side is full of electrons but do you think diffusion should be even considered where strong electric field due to bias voltage due to battery is present there ?
You are right that there are both drift and diffusion currents in the pn-diode. However, due to current continuity in the one-dimensional diode model, the total current (electrons and holes) can be described as the sum of the minority diffusion currents in the quasi-neutral p- and n-regions at the respective depletion zone boundaries. This corresponds to the so-called Shockley model of the diode, which works pretty well at not to high voltages when recombination/generation in the depletion zone can be neglected.
Answered by freecharly on December 6, 2020
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