where did the current flow in pn junction?

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?

About current flow the things u said is about without biasung in that state the drift current and diff current are equal but when a bias voltage is applied things changes and some current get larger depend on polarity of applied voltage ...

u could find more information in device books like Streetman's book

Hi, where can I have a Streetman's book ?

Answer for first question : When we actually join a P and a N junction while fabricating or therwise, due to excess of holes in P and electrons in N region, the recombination process takes place.
What happens in recombination is a hole near the junction is filled by an electron from the junction side of n. Holes can't move, only electrons can.
Hance near the junction recombination leads to formation of depletion layer.
In strict sense of terms it can't be said that current flows only in P or N. But considering the phenomenon just explained it would be more appropiate to say current flows in P region. However as electron travels from n to junction and then to p . Actual current flows thoughout the junction.

Second Question : When an electric field is applied to the diode (PN junction ), in case of forward bias, electrons in N region get stuck to negative plate of source where as electrons from P region are repelled by other end. This repulsion leads to drift of electrons to junction and then to other side leading to current.
The whole movement happens via hole electron combinations.

I hope it helps !
Bye

So can we call the current in the pn juction diode a drift current not a difution current?

I think you are missing out on the basics of electric phenomena. If you can get, read the Electronic devices and circuits book by Nashelsky and Boylstead. its gives simple and clear explanation of what you are looking for.

truebs said:

Answer for first question : When we actually join a P and a N junction while fabricating or therwise, due to excess of holes in P and electrons in N region, the recombination process takes place.
What happens in recombination is a hole near the junction is filled by an electron from the junction side of n. Holes can't move, only electrons can.
Hance near the junction recombination leads to formation of depletion layer.
In strict sense of terms it can't be said that current flows only in P or N. But considering the phenomenon just explained it would be more appropiate to say current flows in P region. However as electron travels from n to junction and then to p . Actual current flows thoughout the junction.

Second Question : When an electric field is applied to the diode (PN junction ), in case of forward bias, electrons in N region get stuck to negative plate of source where as electrons from P region are repelled by other end. This repulsion leads to drift of electrons to junction and then to other side leading to current.
The whole movement happens via hole electron combinations.

I hope it helps !
Bye

Click to expand...

I think there is no current even if you link the PN junction with lead.

First question:
in a pn junction without external fields applied, there are no net currents. We have two distinct currents near the border of the p and n region, which are equal and opposite.
We have an excess of holes in the p region, so they diffuse in toward the n region. The electrons of the n region diffuse toward the p region. These two made the diffusion current (they move in opposite direction, but have different charge sign, so the actually sum).
Due to diffusion, holes leaves negative charged ions in the p region, electrons positive ones in the n region. This creates an electric field (and a consequent drift current) which equals the diffusion current at equilibrium, but has opposite sign.
Second question:
when you apply a forward bias (big enough to overtake the built-in potential) to a pn junction, this cause holes in the p region to flow toward the n one and electrons of the n region to flow toward the n one, which result in a current in the device (a big current, because you have many holes in the p region and many electrons in the n one, i.e. the current is sustained by majority carriers).
When a hole reaches the n zone, it recombines with an electron, the same for electrons entering the p region.

In facts, holes do move. They behave as positive charged particles, even if slower than electrons (about a factor of 3).