Timeline for Change of chemical Potential in forward biased pn-junction
Current License: CC BY-SA 3.0
13 events
| when toggle format | what | by | license | comment | |
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| Oct 13, 2016 at 14:55 | vote | accept | Quantumwhisp | ||
| Oct 13, 2016 at 14:45 | comment | added | freecharly | As holes are just missing electrons, the whole equilibrium system contact plus adjacent semiconductor is an electron system with energy distribution according to Fermi-Dirac statistics with one electrochemical potential. | |
| Oct 13, 2016 at 14:44 | comment | added | freecharly | That the contact and its adjacent n- or p-regions is approximately in thermodynamic equilibrium means both electrons and holes are together in equilibrium and in equilibrium with the electrons of the metal. They are all characterized by the same electrochemical potential in their distribution functions. In doped semiconductors, this includes electrons and holes in the discrete energy states of donors and acceptors in the band gap. The number of electrons and holes in the conduction and valence bands needs not to be equal. | |
| Oct 13, 2016 at 14:13 | comment | added | Quantumwhisp | When you say "the contacts are in thermodynamic equilibrium", then you mean that holes and electrons are in equilibrium, and there is no charge? (for example in an undoped semiconductor, equilibrium would mean there are as mutch electrons as holes?) If this is what you mean by equilibrium, and this is also the situation at the contact, then I get what you mean. | |
| Oct 13, 2016 at 13:50 | comment | added | freecharly | As I pointed out above,when you apply to two isolated electron systems, each in thermodynamic equilibrium, an electrostatic potential difference the electrochemical potentials will differ by this applied voltage but no steady current will flow between them. In the pn-junction the contacts plus n- or p-regions are assumed to be approximately in thermodynamic equilibrium each when you apply a voltage between them, in spite of the current flowing. Therefore the n- and p-regions have (quasi-) electrochemical potentials that differ by the applied voltage, like in the case of the isolated systems. | |
| Oct 13, 2016 at 13:40 | comment | added | Quantumwhisp | The applied voltage is just a condition for the electric potential in the divice to differ by $V$ at the borders of the divice. You could still achieve a constant chemical Potential by having many more particles at the side (n or p) where the potential is lower. I'm sorry that I'm not yet satisfied, I might be annoying for not accepting the answer. Comments are not a fast way to paraphrase what I'm talking about. | |
| Oct 12, 2016 at 14:59 | comment | added | freecharly | The shifted electrochemical potentials of the n- and p-regions remain shifted because you enforce it with the applied voltage. | |
| Oct 12, 2016 at 14:06 | comment | added | Quantumwhisp | Thank you, this is helpfull. But usualy, when the chemical potential not constant, there would be changes in the system, until it is constant (that would be, the system reaches equilibrium). When the voltage is applied, the quasi-electrochemical potentials are shifted, as you said. But then usualy, there will be drift currents that try to restore equilibrium. This is not the case here (the shifted electrochemical potentials remain shifted). Why? | |
| Oct 11, 2016 at 19:19 | history | edited | freecharly | CC BY-SA 3.0 |
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| Oct 11, 2016 at 19:05 | history | edited | freecharly | CC BY-SA 3.0 |
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| Oct 11, 2016 at 18:25 | history | edited | freecharly | CC BY-SA 3.0 |
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| Oct 11, 2016 at 18:14 | history | edited | freecharly | CC BY-SA 3.0 |
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| Oct 11, 2016 at 18:08 | history | answered | freecharly | CC BY-SA 3.0 |