# Equilibrium Distribution of Electrons and Holes

1. Feb 9, 2013

### shayaan_musta

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.

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2. Feb 9, 2013

### Staff: Mentor

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.

3. Feb 10, 2013

### shayaan_musta

@mfb

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.

4. Feb 10, 2013

### Staff: Mentor

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.

5. Feb 10, 2013

### shayaan_musta

Here is another image. sorry friend.

Now you can see the last 4 lines of the first paragraph in the given image.

#### Attached Files:

• ###### equilibrium distribution of electrons and holes.PNG
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6. Feb 12, 2013

### shayaan_musta

Anyone help me

7. Feb 12, 2013

### Staff: Mentor

I don't see any open questions.

8. Feb 12, 2013

### shayaan_musta

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.

9. Feb 12, 2013

### Staff: Mentor

I posted an explanation in post 4.

10. Feb 13, 2013

### shayaan_musta

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.