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Use this tag to ask about band-structure formation in solids, or about how electrons and holes behave inside them.

6 votes

Is conduction band discrete or continuous?

As other have noted, it's discrete but with fine enough spacing to treat as continuous. However I disagree that quantum mechanics is the reason. You see the exact same thing in a classical 1-D chain o …
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5 votes
Accepted

Does the shifting of the Fermi energy level of an intrinsic semiconductor mean that $n \neq p$?

Your equation 1 was derived with an approximation for the Fermi-Dirac integral and was derived for 3D. That is, they used $F_{\frac{1}{2}}\left(\eta_c\right) \approx \frac{\sqrt{\pi}}{2} e^{\eta_c}$, …
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4 votes
Accepted

Fermi level and chemical potential in doped and pure semiconductors

You're right that this can be a tricky point if there is a gap, and I think that a number of common definitions fail in this case. It gets even trickier at zero temperature. Let me give an alternativ …
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4 votes

Why are there electron and hole currents in semiconductor, but only electron current in metal?

As Pieter noted, in some metals, arguably, all the carriers are holes. This can be seen by measuring a material's Hall coefficient, which tells you the effective carrier charge, and for a number of me …
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3 votes
Accepted

Does crystalline silicon have a higher (~3.0 eV) band gap than amorphous Si (~1.75 eV)? Or l...

The band gap of crystalline Si at 300 K is 1.12 eV. Here is an authoritative source for band structure information. Crystalline silicon is an indirect band gap semiconductor. Doping does not change th …
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3 votes
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Zone unfolding for a hexagonal lattice

Right, so it turns out this is quite simple. See the figure below. (a) shows the 1st BZ resulting from the hexagonal and rectangular unit cells of the honeycomb lattice. Note that the hexagon has twi …
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2 votes

How do charge carriers move thermal energy? (Peltier effect)

The heat of a solid is related to the energy contained in the solid. Hotter solids have more energy in them. Where is the energy in the solid? It's in the atoms and charge carriers moving/bouncing ar …
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1 vote
Accepted

How to read some certain band diagrams?

Both confusing diagrams show heterostructures (i.e. one device containing different materials), and the different materials can have very different properties. In the first figure: At the left is a m …
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1 vote
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Energy Bands Question

I would answer "no", but it depends what you mean. An electron going from the conduction to the valence band eliminates both a conduction band electron and a valence band hole. Both helped with conduc …
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1 vote

What is the cause of formation of indirect band gap in semiconductors?

I don't think we should be so quick to say that there's no way to know without doing a calculation. In some cases, there are rules of thumb: https://journals.aps.org/prb/abstract/10.1103/PhysRevB.98.2 …
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1 vote

Group Velocity Formalism vs. Current Operator Formalism in band theory

Can the "well-known properties" be developed using free particles? (I think that the answer should be "yes".) Because the two equations are the same for free particles. For free particles: $$\epsilon\ …
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1 vote

What can we learn from a band structure diagram?

Depending on what is shown in the band diagram, you can see if it's a topological insulator. Most band diagrams just show what's going on in the bulk material -- what you'd get with an infinitely larg …
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1 vote
Accepted

Explanation of the concavity of conduction band and valence band of semiconductors at $k=0$

Band structures do all sorts of weird things. Just look at Si if you want a conduction band that has the "wrong" concavity. That said, the concavity you describe is common. By definition, it's true fo …
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1 vote

Is it possible to draw an EK diagram for the infinite square well?

You asked two separate questions: Is it possible to draw an EK diagram for the infinite square well? No. Such a diagram only makes sense if the potential is periodic, and that's not the case for an …
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1 vote

Does the Thomas-Fermi screening length formula only apply to metals?

No, it applies whenever there are free charges. So, it applies to semiconductors too (especially doped ones) or even insulators if you can heat them up enough without melting them... EDIT: by way of e …
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