Q) Explain the formation of depletion layer and potential barrier in a p-n junction - Physics - Semiconductor Electronics Materials Devices And Simple Circuits

Question

Q) Explain the formation of depletion layer and potential
barrier in a p-n junction ?

Gaurav Joshi · Answer

If one side of crystal pure semiconductor
Si(silicon) or Ge(Germanium) is doped with acceptor impurity atoms
and the other side is doped with donor impurity atoms , a PN
junction is formed as shown in figure P region has high
concentration of holes and N region contains large number of
electrons

What is Depletion Layer of Pn Junction?
As soon as the junction is formed, free
electrons and holes cross through the junction by the process of
diffusion During this process , the electrons crossing the junction
from N- region into P-region , recombine with holes in the P-region
very close to the junction Similarly holes crossing the junction
from the P-region into the N-region, recombine with electrons in
the N-region very close to the junction Thus a region is formed,
which does not have any mobile charge very close to the junction
This region is called the depletion layer of pn
junction
<img title="depletion layer pn junction"
alt="depletion layer pn junction" src=
"http://image%20wistatutor%20com/content/feed/tvcs/pn20junction201_0%20JPG"
width="400" height="178">
In this region, on the left side of the
junction, the acceptor atoms become negative ions and on the right
side of the junction, the donor atoms become positive ions as shown
in figure
Function of Depletion Layer of Pn Junction :
An electric field is set up, between the
donor and acceptor ions in the depletion layer of the pn junction
The potential at the N-side is higher than the potential at P-side
Therefore electrons in the N- side are prevented to go to the lower
potential of P-side Similarly, holes in the P-side find themselves
at a lower potential and are prevented to cross to the N-side Thus,
there is a barrier at the junction which opposes the movement of
the majority charge carriers The difference of potential from one
side of the barrier to the other side of the barrier is called
potential barrier The potential barrier is approximately 0 7V for a
silicon PN junction and 0 3V for germanium PN junction The distance
from one side of the barrier to the other side is called the width
of the barrier, which depends on the nature of the
material

Q) Explain the formation of depletion layer and potential barrier in a p-n junction ?

What is Depletion Layer of Pn Junction?

Function of Depletion Layer of Pn Junction :