How Does Electric Field Influence Current Flow in a PN Junction Diode?

[020170]

when it comes to pn junction in diode, p and n are doping semiconductors.

if P and N semiconductor are contacting each other,

some holes in P and some electron in N are combined. that is, they are recombined.

this recombination caused the current, very small.

I was wondering that where did this current flow. did it flow through N? or P?



Another Question : in depletion layer, when the current due to the free carrier

diffusion equals the current caused by the electric field, and the pn junction

reaches equilibrium. I knew that electric field make the current
when metal like Cu is moving back and forth between electric field.

but in pn junction, how did electric field make the current?

 

[Gokul43201]

when it comes to pn junction in diode, p and n are doping semiconductors.

if P and N semiconductor are contacting each other,

some holes in P and some electron in N are combined. that is, they are recombined.

this recombination caused the current, very small.

I was wondering that where did this current flow. did it flow through N? or P?

Under equilibrium, there is no current in an unbiased PN junction. The recombination is simply the "annihilation" of free electrons by free holes near the interface, due to diffusion from a difference in chemical potential. You may choose to refer to this recombination process in terms of a transient diffusion current, in which case, a positive transient current would have flowed from the p-type to the n-type SC.

Another Question : in depletion layer, when the current due to the free carrier

diffusion equals the current caused by the electric field, and the pn junction

reaches equilibrium. I knew that electric field make the current
when metal like Cu is moving back and forth between electric field.

but in pn junction, how did electric field make the current?

The process is the same, whether it's a metal or semiconductor. The electric field exerts a force on the free charge carriers in the conduction band. The result of this force (along with phonon/impurity scattering) is a current along the direction of the field.

The only real differences are in the nature of the majority charge carriers (in pure Cu, these are electrons; in p-type Si, these are holes) and the mechanism by which the conduction band is populated.

 

[ravenprp]

The pn junction in a diode is a crucial component that allows for the flow of current in one direction, while blocking it in the other. When P and N semiconductors are in contact, as you mentioned, some holes in P and electrons in N combine and create a depletion layer. This depletion layer acts as a barrier for the majority carriers (holes in P and electrons in N) to cross over and recombine. However, there are some minority carriers (electrons in P and holes in N) that can still cross over and contribute to a small current flow. This current flow is due to diffusion, as the minority carriers move from the higher concentration region to the lower concentration region.

To answer your question about where this current flows, it actually flows through both the P and N regions. The minority carriers move from one region to the other, creating a small current flow. However, the majority carriers are unable to cross over and thus do not contribute to the current flow.

In the depletion layer, as you mentioned, there is a balance between the current caused by diffusion and the current caused by the electric field. The electric field is created due to the difference in the doping levels of the P and N regions. This electric field pushes the majority carriers towards the depletion layer, while simultaneously pulling the minority carriers towards it. This creates a barrier that prevents further diffusion and results in equilibrium.

To understand how the electric field creates the current, it is important to remember that in a diode, there is a built-in potential barrier due to the difference in doping levels. This barrier prevents current flow in one direction, but when a forward bias is applied, it reduces the barrier and allows for current flow. This is how the electric field in the depletion layer makes the current flow in a pn junction in a diode.

In summary, the current flow in a pn junction in a diode is due to the movement of minority carriers, while the electric field in the depletion layer plays a crucial role in creating a potential barrier and allowing for current flow in one direction.