MOS Capacitor - Accumulation Mode Explained

/ edmundsj
If you want to see more of these videos, or would like to say thanks for this one, the best way you can do that is by becoming a patron - see the link above :). And a huge thank you to all my existing patrons - you make these videos possible.
MOS capacitor in accumulation mode. What accumulation mode means, what the band diagram looks like in the semiconductor as well as the full MOS structure, and what voltage we need to apply to put the MOS capacitor into accumulation mode.
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.

[@shantisnijder3598]

"..wait how did i draw it" ... *restarts*

[@TestMarksman]

You just saved my semester. Thank you very much.

[@svartheim500]

he saved my degree

[@BirdNaito]

Great video, Jordan!

[@user-dx1fz6eq9d]

The video really helps a lot!! Thank you!

[@user-fk9mu3py2z]

Thanks for awesome lecture for my winter vacation👍

[@shuvamdas4334]

Wow what an explanation we need cool teachers like you in our Universities

[@Carl-zj1lz]

Great video, thanks!

[@amrohendawi6007]

perfect explanation !!!

[@abdolw3682]

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

[@samermohamed9082]

Hey, I love your videos. They are extremely helpful for my semiconductors course. We're also using Neamen. I was wondering if, in the future, you could share text references to accommodate people like myself who like to learn through a combination of books and KZbin videos. Thanks! Keep the excellent videos coming, they are much appreciated!

[@NicolasSchmidMusic]

he is following the book from Neamen called semiconductor physics and devices. Just google it the pdf is online

[@samaalobidi1070]

Thnx sooooo much U re the only one that i can understand from Thnx again ♥️♥️

[@Ann-jj4qe]

Shouldn't the bending direction of p-type mos capacitor in accumulation mode be up?

[@christophergeralddeungria1455]

Thank you for saving me and my family from Semicons

[@JordanEdmundsEECS]

XD my pleasure

[@reihanehafghahifarimani115]

thank you! these videos are great! I'm new to semiconductors and I need it to understand my project. I have a question though why the Fermi level never changes? the nature of the Fermi level is the probability so shouldn't it change with applying a voltage?

[@lidijxyz]

It does change, check out the definition and derivation of Fermi level, for example, it depends linearly on temperature But on itself is a function derivativated from fermi-dirac distribution

[@salihkapicioglu]

Hello, thanks for the videos. By the way which tools (software & hardware) do you use for these videos?

[@JordanEdmundsEECS]

Thanks :D currently I use an iPad Pro (12.9”) running Duet Pro at a resolution of 2048x1536 at 60fps, the software I use is SketchBook from Autodesk and OBS Studio for the screen capture.

[@Misterioso9000]

Why i dont had a teacher like you???

[@pl5094]

What is the difference between accumulation mode and forward biasing?

[@sea-pl2mf]

thank you

[@yakovhammer5739]

What happens when V=0 ? would that also be considered Accumulation Mode?

[@xltian4368]

the band diagram discussed dring 6:30 is p-Gate on n-Substrate, it got me confused for quite a while. However, Great Job on doing this video. Thanks a lot.

[@xltian4368]

Sorry, I was wrong above. It took me few times of watching this video to understand the 'intrinsic band bending'.

[@ajayponasanapalli9513]

@@xltian4368 can u explain in detail what happened there? I didn't get it

[@NicolasSchmidMusic]

I don't really get why there is band bending without any applied voltage. And between 6:22 and 7:20 you talk about these work function as if you already talked about, but I can't find where, can you help me?

[@Thexxidoxx]

happened to me too. The video we are looking for is "MOSFET Band Diagram Explained".

[@hasancanar3125]

As you said semiconductor was grounded, how did you apply voltage on it ?

[@JordanEdmundsEECS]

Great question! What matters here is the *relative* voltage of the body and the gate, so applying a positive voltage to the body is the same as applying a negative voltage to the gate.

[@himanshuful]

Thanks Jordan for your semiconductor lecture series. They are really good. Can you pls confirm the energy band bending in accumulation mode for n-MOS (p-type substrate). Shouldn't it be upward bending in the band diagram @6:12 in video

[@xltian4368]

it is the intrinsic band bending @6:12. It took me quite a while to figure out.

[@704nazmusshakibneshat9]

nice video sir !! Thanks

[@dannchan00]

I have two questions that I found myself hard to understand or confused all the time. I try to make a statement from my understanding and Dr. Jordan please correct me or guide me with proper principle. 1)The band diagram is drawn in respect of electron energy, so applying positive voltage (containing excess holes) at a particular region will drop any band diagram of that region but apply -ve voltage (containing excess electron) will increase any of the band diagram? 2)I thought the Ef is a constant at equilibrium (contact) , means it doesn't change and form a straight line for all materials (oxdie,metal and SC ) contact. Hence by applying voltage potential, it can be shifted?

[@supravatdebnath9464]

Your assumption regarding the energy bands being drawn in terms of electronic potential is correct. More -ve voltage means we go up in energy in the band diagram and vice versa. Regarding your 2nd question, on the application of voltage, the built-in potential developed in equilibrium condition gets reduced or increased depending on the polarity of the bias.

[@supravatdebnath9464]

By applying a voltage on the gate we are shifting the Fermi level of the gate metal (or polysilicate). This creates a difference between the Fermi level of the gate metal and that of the semiconductor. Difference in fermi-level between the two encourages all the subsequent charge distribution phenomena and the band bending. Applying external bias takes a system out of equilibrium so fermi levels can change.

[@rajgandhi4042]

From 10:50 you mention one thing wrong that if phi Ms is positive, line moves up when we move from left to right but it should be opposite. Please answer what is actually the answer

[@JordanEdmundsEECS]

Sure! I believe that is correct, phi_ms refers to the difference in the Fermi levels before you bring together the semiconductor and the metal. A positive phi_ms means the Fermi level of the metal is higher energy (semiconductor is lower energy), so when the Fermi levels meet electrons will jump from the metal to the semiconductor, and you will end up with an E-field that points to the right, which yields the energy profile in the video.

[@rajgandhi4042]

In your explanation whose work function is more metal or semiconductor?

[@rajgandhi4042]

@@JordanEdmundsEECS your definition of phi Ms is wrong. It is energy required to move electron from Fermi energy to free space. And according to this phi Ms in this case will be negative. I am referring sung-mo-kang and In that it is mentioned like this what I am saying

[@JordanEdmundsEECS]

You are correct about the sign, phi_ms in this case should be negative. The metal Fermi energy is higher in energy, but its work function is smaller. Phi-ms is defined in terms of these work functions, see Neamen p. 383.

[@rajgandhi4042]

At 8:16 what is concept of draging band? Plz explain

[@JordanEdmundsEECS]

It’s just a way of visualizing what’s going on. Imagine you take your hand, grab the edge of the band structure, and physically drag it up. This is going to cause everything to start slanting.

[@rajgandhi4042]

@@JordanEdmundsEECS ??

[@user-ej3rq8pv8l]

What does "undo" mean?

[@joxa6119]

Yes what it actually means by it? @Jordan Edmunds

[@LTF-uj1yc]

Why is it bend downwards when no voltage is applied?🙃

[@LTF-uj1yc]

Great explanation otherwise :D

[@tjcogger1974]

It bends downwards when a positive voltage is applied. With no voltage, the bands are just flat.

[@habebamahmoud6843]

اللهي تنستر

[@renatoberaldo2335]

Your english accent seems like you are not a indian youtuber... lol

[@user-fk9lk6rk6f]

full of stupid mistakes. I could be the stupid one though.

[@tjcogger1974]

You are.