Position of Fermi level in the semiconducting material

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alok_shukla1
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Position of Fermi level in the semiconducting material

#1 Post by alok_shukla1 » Sun May 29, 2022 2:04 am

Dear Experts,
I have one doubt about the position of the Fermi level in semiconductors. I plotted the band structure of one 2D material having a band gap ~1.24 eV. I am getting the Fermi level in the middle of the valance and conduction bands. But I noticed in the literature that the Fermi level is coming on the top of the Valance band in the band structure plot for the same material (using the VASP code only).
Which one is the correct way of representing the band structure plot? If the second way is correct then how can I chage my Fermi level.
Please give your helpful suggestions about it.

martin.schlipf
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Re: Position of Fermi level in the semiconducting material

#2 Post by martin.schlipf » Mon May 30, 2022 7:15 am

The Fermi energy is not uniquely defined for semiconducting materials. We work on a more reliable algorithm that will be more deterministic, but as of now (VASP 6.3.1), the Fermi energy will end up at an arbitrary energy in the middle of the gap. The particular algorithm used will make energies towards the bottom of the gap more likely, but that is not guaranteed.

Typically one would then align the Fermi energy at the valence band maximum as a post processing step when preparing the figure for publication.

Martin Schlipf
VASP developer


alok_shukla1
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Re: Position of Fermi level in the semiconducting material

#3 Post by alok_shukla1 » Mon Jun 13, 2022 8:46 am

Dear Expert,
Thank you so much for sharing this valuable information.
Now, my doubt is clear.

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