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Equilibrium Distribution of Electrons and Holes

by shayaan_musta
Tags: distribution, electrons, equilibrium, holes
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shayaan_musta
#1
Feb9-13, 01:53 PM
P: 184
Hello. I was studying the Semiconductor and I am confused with this diagram.
I have attached the diagram. Please tell me briefly what does this diagram say. So that I could ask further. I have confusion with this diagram. I don't want to be specific so that you describe the whole diagram briefly and I will try to understand it.

Thank you.
Attached Thumbnails
Equilibrium distribution of electrons and holes.PNG  
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mfb
#2
Feb9-13, 02:18 PM
Mentor
P: 11,928
fF(E) is the probability that a state is occupied, as determined by the Fermi distribution (left=0, right=1). It is close to 0 for states of high energy (top part of the plot) and close to 1 for states of low energy (bottom).
gc is the density of states in the conducting band with that specific energy - it is zero at Ec and increasing for higher energy.

To find the number of electrons with a specific energy, you multiply both functions, and get the shaded area. Its area is (proportional to) the total number of electrons.

gv is the same in the valence band.
shayaan_musta
#3
Feb10-13, 01:57 AM
P: 184
@mfb

Thank you for your kind reply. Here is another image.
I am confused with a sentence "We note previously that the function f(E) for E>EF is symmetrical to .........", last four line of the first paragraph.

Would you please help me in understanding how f(E) for E=Ef+dE is equal to the function 1-f(E) for E=Ef-dE.

Thank you.

mfb
#4
Feb10-13, 07:27 AM
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P: 11,928
Equilibrium Distribution of Electrons and Holes

I don't see another image.

Close to the Fermi energy and for small temperatures (always true in semiconductors), the function is nearly point symmetric with f(EF)=1/2 as symmetry point.
That relation is just another way to express this symmetry.
shayaan_musta
#5
Feb10-13, 10:16 AM
P: 184
Here is another image. sorry friend.

Now you can see the last 4 lines of the first paragraph in the given image.
Thank you for your reply.
Attached Thumbnails
equilibrium distribution of electrons and holes.PNG  
shayaan_musta
#6
Feb12-13, 04:52 AM
P: 184
Anyone help me
mfb
#7
Feb12-13, 09:41 AM
Mentor
P: 11,928
I don't see any open questions.
shayaan_musta
#8
Feb12-13, 01:30 PM
P: 184
Hello friend.
What do you mean by open question?
I am asking you to clear the last four line of the first paragraph from the attached image.
Thank you.
mfb
#9
Feb12-13, 03:02 PM
Mentor
P: 11,928
I posted an explanation in post 4.
shayaan_musta
#10
Feb13-13, 07:19 AM
P: 184
I read your post several times and I got what you have said. Thank you. It is cleared now. I hope you will help me next time if I post another thread for help.

Thank you.


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