Semiconductor -- Conduction and Valence bands

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SUMMARY

This discussion focuses on the conduction mechanisms in semiconductors, particularly silicon. It highlights the role of energy bands, specifically the conduction and valence bands, and the excitation of electrons when energy is applied. The 0.7V threshold mentioned is clarified as related to PN junctions rather than direct conduction. Key resources referenced include Chenming Hu's semiconductor textbook, which provides detailed explanations of electron motion and drift in semiconductors.

PREREQUISITES
  • Understanding of semiconductor physics, particularly energy bands
  • Familiarity with PN junctions and their characteristics
  • Knowledge of electron mobility and current flow in materials
  • Basic concepts of potential difference and its effects on charge carriers
NEXT STEPS
  • Read Chenming Hu's semiconductor textbook, focusing on section 1.3 for a deeper understanding of energy levels
  • Study Chapter 2 of the same textbook, particularly section 2.2, to grasp electron drift in semiconductors
  • Research the principles of PN junctions and their role in semiconductor conduction
  • Explore the concept of hole flow and its implications in semiconductor physics
USEFUL FOR

This discussion is beneficial for students and professionals in electrical engineering, particularly those studying semiconductor devices and their operational principles.

pj33
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TL;DR
How does a semiconductor conducts
I am a new to this and I try to understand the basics.
So initially once the atoms of silicon come together to form a solid, due to Pauli law no electrons can exist in the same energy state,thus many energy states are formed which together make the bands.

My problem starts at this stage where I try to understand the conduction in macro and micro state.
1) In the silicon the valence and conduction band have some energy difference, but once there is some energy input, the electrons get excited if there is sufficient energy, then they move to the conduction band (does this energy correspodn to the 0.7V required by the semiconductors such as diodes, to conduct?)
2) Can someone explain me the electron motion once the potential difference is applied ( I was shown a picture same as the first picture here https://ecee.colorado.edu/~bart/book/eband4.htm). I was told that the electrons roll down because there available energy levels, but I can't see how this work.
3) Then, once the potential difference is applied the electrons move towards the positive electrode thus current flow and the holes flow towards the negative electrode (does the flow of holes cause anything?)
4) What happens to the electrons left in the valence band?

Thank you in advance!
 
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pj33 said:
Summary:: How does a semiconductor conducts

I think you should reference Chenming Hu's excellent & free semiconductor textbook.

For 1: You're close but your terminology is wrong. Read section 1.3 very closely. The 0.7V is something else. You cover it when you review PN junctions.
https://www.chu.berkeley.edu/wp-content/uploads/2020/01/Chenming-Hu_ch1-3.pdf

For 2 to 4: Chapter 2 of has an excellent description of drift. I think especially section 2.2 will help you.
https://www.chu.berkeley.edu/wp-content/uploads/2020/01/Chenming-Hu_ch2-2.pdf
 
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