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P-N junction diode

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1.  WHAT IS P-N JUNCTION DIODE?
=>  it is a semiconducor that carries current only in one direction.


2. HOW IS A P-N JUNCTION FORMED?

    => when you attach a p-type and an n-type semiconductor then nothing happens. but if one side of a semiconductor chip is positively doped and another side is negetavely doped then it forms a diode that carries current in only one direction.


here are a few phemenon that you neeed to understand to expalin the working of barrier potential

A. DIFFUSION and DEPLETION LAYER

=>  the holes form p-doped region  move to  n-doped region through diffusion.


the holes and free electrons combinde at the junction to form form immobile charge. this lead to formation of a layer that is depleted of free charge carriers called the depletion region.

due to formation of depletion layer, the diffusion stops before all free charges are diffused.

B. BARRIER POTENTIAL

=> at the junction there are immobile charges seperated by a distance.

this leads to froamtion of electric field from N-type to P-type.

to pass through this field the charges need a minimum potential called the barrier potential.

C. DRIFT CURRENT AND DIFFUSION CURRENT


1. majourity charge carriers move due to diffusion pressure, thus causing diffusion current

2. minority charge carriers move in opposite direction due to electric field, thus causing drift current.

at equlilbrium,

drift current = diffusion current