Can someone explain, why free electrons in N - side don't continue to combine with holes (positive charges) in depletion region?

 

hi lin,
This link explains how the PN barrier charge builds and neutralises the potential differnce.

E
https://www.google.com/search?client=firefox-b-d&q=PN+junction+barrier+build+up


Clip:
In a P-N junction, a barrier potential builds up due to the diffusion of charge carriers (electrons and holes) across the junction, leading to the formation of a space charge region (depletion region). This region creates an electric field that opposes further diffusion, establishing an equilibrium where the movement of charge carriers across the junction is minimized

 

hi lin,
This link explains how the PN barrier charge builds and neutralises the potential differnce.

E
https://www.google.com/search?client=firefox-b-d&q=PN+junction+barrier+build+up


Clip:
In a P-N junction, a barrier potential builds up due to the diffusion of charge carriers (electrons and holes) across the junction, leading to the formation of a space charge region (depletion region). This region creates an electric field that opposes further diffusion, establishing an equilibrium where the movement of charge carriers across the junction is minimized

it means that free electrons in N type are pushed back by electrons in depletion region and cannot continue to diffuse?

 

hi,
Think of when an electron/hole combination occurs at the junction of the PN material.
It will result in a reduction of the electric field strength across the junction, after a number of such combinations, the field strength across the junction will be reduced to close to zero, so no more electrons will be 'attracted' across the PN junction barrier.

E
Check out this PDF.
Clip:
At the same time, the holes
in the P material diffuse across the junction into the N material and are filled by N
material electrons. This process, called junction recombination, reduces the number
of free electrons and holes in the vicinity of the junction. Because there is a depletion,
or lack of free electrons and holes in this area, it is known as the depletion region.

 

hi,
Think of when an electron/hole combination occurs at the junction of the PN material.
It will result in a reduction of the electric field strength across the junction, after a number of such combinations, the field strength across the junction will be reduced to close to zero, so no more electrons will be 'attracted' across the PN junction barrier.

E
Check out this PDF.
Clip:
At the same time, the holes
in the P material diffuse across the junction into the N material and are filled by N
material electrons. This process, called junction recombination, reduces the number
of free electrons and holes in the vicinity of the junction. Because there is a depletion,
or lack of free electrons and holes in this area, it is known as the depletion region.

Do you know why electrons marked with red arrow not combine with + holes(normally they attract each other)?

 

hi,
Does this image explain?
E

 

hi,
Does this image explain?
E
View attachment 347840

why no charges, they mark with ''+'' and ''-'', mean positive ion and negative ion?

 

hi,
Does this image explain?
E
View attachment 347840

Why free electrons in N region not move to positive holes in barrier region to combine with them more??

 

hi,
Initially, when the PN junction is formed, you have a Silicon interface formed by Boron atoms, which are capable of adding and a free electron to themselves. On the other side of the Silicon PN junction, you have a Phosphorous based material which has a loosely bound free electron.
The Boron and Phosphorus atoms share that electron, so you have effectively an electrically neutral pair, this happens along the whole PN interface, so you now have a neutral charge barrier between the PN materials, formed of neutral charged atom pairs.

This barrier effectively blocks any further Boron/Phosphorous electron sharing, as the Boron/Phosphorous holes/electrons in the remainder of the PN materials are no longer in direct physical contact in order to allow the free electron to be shared.

The PN junction now will require an external voltage in order for a current to flow through the junction.

E

 

hi,
Initially, when the PN junction is formed, you have a Silicon interface formed by Boron atoms, which are capable of adding and a free electron to themselves. On the other side of the Silicon PN junction, you have a Phosphorous based material which has a loosely bound free electron.
The Boron and Phosphorus atoms share that electron, so you have effectively an electrically neutral pair, this happens along the whole PN interface, so you now have a neutral charge barrier between the PN materials, formed of neutral charged atom pairs.

This barrier effectively blocks any further Boron/Phosphorous electron sharing, as the Boron/Phosphorous holes/electrons in the remainder of the PN materials are no longer in direct physical contact in order to allow the free electron to be shared.

The PN junction now will require an external voltage in order for a current to flow through the junction.

E

Can you shortly explain?