MOSFET Band Diagram Explained

/ edmundsj
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In this video I introduce the complete MOSFET band diagram, including the energy band of the metal (or polysilicon), oxide, and semiconductor. I introduce the concept of the vacuum level, and the metal/semiconductor work function. Then I explain how to create the full band diagram, and talk about how central band bending will be as a concept in drawing it. In the next video, I will draw out the full band diagram, with band bending in each region.
This is part of my series on semiconductor physics (often called Electronics 1 at university). This is based on the book Semiconductor Physics and Devices by Donald Neamen, as well as the EECS 170A/174 courses taught at UC Irvine.
Hope you found this video helpful, please post in the comments below anything I can do to improve future videos, or suggestions you have for future videos.

[@qwweeerqqr12]

I absolutely cannot thank you enough for this video series

[@JordanEdmundsEECS]

Thanks 😌 Anything in particular you enjoyed?

[@JordanEdmundsEECS]

There is an error at 7:39, Phi(ms) should be phi(m) - phi(s), where phi(s) includes both chi(s) AND the difference between the conduction band and the fermi level of the silicon.

[@prashantupadhyay6019]

thanks for this statement, i was clueless for 2 minutes

[@sigangsabaglari3606]

I was wondering the same thing yesterday, fortunately i checked the comment section today.

[@xxzeroxx8417]

Great explanation sir!!!

[@yewedmund]

This video should go before the last three MOS capacitor videos on the playlist

[@abdolw3682]

Thank you very much, you are life saver, so much hearts ♥️

[@playoffrondo8927]

As a sophomore lab intern this helps alot thanks soo much

[@aminnonplus]

Thank you !

[@pushpaselvarasu4811]

Thank you so much, for your wonderful taught. In this part you explained about P type semiconductor. Can you explain about the n type semiconductor band diagram in MOSFET.

[@aakashgupta4478]

Thanks A Lot,,,,,u Saved my time

[@robpearson2160]

Flat Fermi Energy level in equilibrium analogy is that when all materials at different temperatures are brought together there is energy transfer (some heat up, some cool down) but they all reach the same temperature (Thermal Equilibrium). The band bending at equilibrium shows the relative energy transfer that has occurred.

[@dannchan00]

Question regarding to vacuum lvl. I was wondering let say we push to the metal or semiconductor by applying super high negative voltage, the electron will be completely striped, will the electron come back when energy drop back or the metal /SC become useless respectively?

[@samaalobidi1070]

Thnx so much

[@reihanehafghahifarimani115]

I think in ur diagram if u apply a positive voltage to ur gate the Fermi level would be lower than the semi one

[@user-ev9od1eo1h]

why the fermi level of semiconductor is lower than metal at the beginning? I think it should be inverse

[@ly3282]

how come the energy needed to strip electrons in metal is higher than it is in semiconductor according to band diagram at 6:11? why qΦm is larger than qXsi?

[@JordanEdmundsEECS]

Excellent question. It doesn’t have to be. The metal work function depends on the metal in question, and can actually be larger or smaller than that if silicon.

[@ly3282]

@@JordanEdmundsEECS thank you very much sir，is there any textbook having detailed derivation related to this topic?which textbooks are you using for reference?

[@Himang_02]

What will happen if Vg =0. Will there be band bending

[@tusharpatle829]

If phi(ms) = phi(m) - chi(s) then how is that equal to E(f) for metal - E(f) for semiconductor. Is it that the chi(s) is the difference between vacuum level and Fermi level for semiconductor

[@JordanEdmundsEECS]

Tushar Patle ph(ms) is equal to phi(m) - phi(s), and phi(s) includes both chi(s) and the difference between the conduction band edge and the fermi level.

[@abebe7017]

@@JordanEdmundsEECS Thank you very your videos. Can you please update the equation with all variables included? I could not understand the equations you describe in words in your previous comments. Thanks again!

[@nihalagrawal4646]

Why in oxide band diagram valence band is way down????

[@JordanEdmundsEECS]

Because silicon dioxide is just like silicon in that it has a band gap, it’s just a HUGE one (like 9eV).

[@shinzon0]

also a metal's conduction band in the simple model is filled to the fermi level... EC and EF do not coincide

[@rishivarrey1176]

why the entire fermi level is equal to that of metal ?

[@JordanEdmundsEECS]

Rishi Varrey When a given system is at equilibrium (for example a MOSFET) the fermi level is constant throughout. Since the metal’s fermi level does not move (it’s got so many electrons) the silicon fermi level has to change to be the same as the metal’s.

[@tejaswininivarthichandrash597]

@@JordanEdmundsEECS but the Fermi level of the semiconductor too doesn't move by band bending right? Band bends only changes other energy band levels except the Fermi level

[@gracecullen9623]

bop

[@shinzon0]

workfunction is not the same as affinity... your definition of phi_ms is wrong. you must go from EF to E0, not from EC to E0, hence phi_m - phi_s

[@jefferyaustin1571]

poor explanation and confusion

[@JordanEdmundsEECS]

Thanks for the feedback! Anything specific you found confusing?