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I am reading this page about electron energy concept terminology.

I am trying to apply that for the pn junction in equilibrium below.

Could anyone help me to see if I get it correctly?

C = Electric potential = built-in potential

B = Internal chemical potential of electrons = 0

(because Fermi level is constant through the junction)

A = Total chemical potential of electrons = B + C = built-in potential

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You said "Fermi level is constant throughout the junction" - that's correct. But fermi level is "A" (see top right in the table). So A is constant (you can set it to zero if you like). B is not constant.

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  • $\begingroup$ Thank you very much for the answer. Could you tell me what is B in this case? If it is not constant then B is not zero so what is wrong here? $\endgroup$
    – emnha
    Commented Jun 23, 2016 at 1:12
  • $\begingroup$ Also, could you comment about the answer of Prof. Rehan Kapadia on the page? quora.com/… There are two problem I am confused relating to the answer: 1. Why did he say that all the answers relating to contact potential are incorrect? 2. If I understood him correctly, in pn junction the Fermi level is same everywhere so the voltage meaaused will be always zero regardless of whether there are contact potential or not. Is this right? $\endgroup$
    – emnha
    Commented Jun 23, 2016 at 1:50
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    $\begingroup$ You said B is zero. But it's not. You didn't say why you believe B to be zero, so I can't explain "what is wrong" in any detail. $\endgroup$
    – Steve Byrnes
    Commented Jun 23, 2016 at 16:54
  • $\begingroup$ See also physics.stackexchange.com/questions/86843/… $\endgroup$
    – Steve Byrnes
    Commented Jun 23, 2016 at 16:55
  • $\begingroup$ Thank you. From the description above, B seems to be the difference in work function of n and p semiconductor. But I am confused about the Fermi level in A and Fermi level in B. What is the difference between them? I infer that the Fermi level in B is the Fermi energy level when p and n semiconductor haven't brought together in contact while the Fermi level in A is the Fermi energy level when they are in contact. Am I correct? $\endgroup$
    – emnha
    Commented Jun 24, 2016 at 3:44

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