Although it's a 5 mins video but it explains a lot and what I mean by a lot doesn't just means "a lot" but it means A LOT! Thanks for the Exceptional work, and keep nourishing our minds with that great way of putting up science
As a material and nano tech engineer it helped a lot thank you so much! This 5 min video was definitely more effective than the 2 hours lesson I took at uni
The question is why do course staff, who are paid for the job, fail to explain this concept as clearly and simply as this TH-cam channel does! Thank you for the video!
true true on the course teachers' defense, they rly cannot explain the topics with the help of such intuitive animations shown in youtube videos but still overall I feel youtube just does a better job at teaching us lol
You probably gave no indication that you didn't understand the material. It's adult learning, so if you don't get the most out of what you are paying for then that's on you. Secondly, there is a bit of confirmation bias in your statement. You have obviously received several hours of face to face tuition and have tried to read your course material in your own time, yet you give 100% of the credit to this video only? Do you think you would have understood everything about diodes if you had just watched this once?
We hope this video was helpful! We have a couple more videos on how diodes/PN junctions work when forward and reverse biased, we recommend you go check them out as well. We also have a wide variety of other tutorials on semiconductors, so explore our channel if you have any more questions on this topic. If helpful, we have the transcript for this video on our website here: www.circuitbread.com/tutorials/how-does-a-diode-work-part-1-the-pn-junction Take care!
after watching many videos, this series on transistor fundamentals is the best so far. The animation is clear and the speaker makes perfect sense. Subscribed.
This was so helpful. I have my physics full syllabus grade 12 exam tomorrow and God semiconductors were one of the most confusing chapters...That is until I watched your videos Thank you so much. The concept is crystal clear
This was by far the most intuitive explanation of band diagram of pn junction I have seen. Thanks brother. Just a minor nit pick in the animation It would have been more clearer to specify that movable charge carriers cross the pn junction and ionize the fixed carriers on the other side So the depletion region is filled with ionize fixed carriers but you showed that carriers were moving during the formation of depletion region, which I guess shouldn't happen in reality But regardless this was a fantastic video thanks
The best explanation for pn junction diode. Hey everyone, I wanted to praise CircuitBread for creating an incredibly helpful video. The content was so informative and well-explained. I'm sure it helped many others as well. Thank you for taking the time to share your knowledge and expertise!.
Thank you for these lectures, it is great to have multiple sources of information, but it is still a confusing topic. so why aren't those negative charges (electrons) change places with positively charged... what exactly? Ions? holse?
First, let me thank you for the good videos. But in this one, I wonder if it's factually correct. What I have in mind specifically is the energy diagrams at 2:30. There is not enough space to explain in detail but in a nutshell: the valence band of the p-region can be above or below of valence band of the n-region, depending on used materials. Take for example P atom with electron configuration [Ne]3s^2 3p^2 => 5 electrons with principal quantum number = 3 vs B atom (you named it as p-type impurity) with [He] 2s^2 2p^1 => 3 electrons with PQN=2. So electrons in the B valence shell have even lower energy than those in P. Ga or In atoms would work (see periodic table). Second and more importantly - when elections recombine on PN junctions the electron energy needed to escape from P atom DOES NOT change. Bands are not moving anywhere contrary to your statement in 3:41. These are still the same atoms. P atoms further in the n-region are willing to give up the extra electron same as before. These may either recombine with holes in the p-region closer to the PN junction (causing hole current) or may try to penetrate to n-region and recombine with the n-region hole. The only problem is really that there is already a barrier of earlier recombined negative ions of B/Ga/In atoms. These exert a repelling force on free electrons coming from the n-region according to Culomb's law (as you correctly explain in 2:00). In a nutshell to understand PN junction it's critical to understand 2 distinct forces - 1) Culomb's law and 2) the proclivity of electrons to fill the atom valence shell in some patterns which is key for understanding chemical bondings, the periodic table, and chemical element properties. Also, I think there is no conduction band but rather conduction space simply for all electrons with enough energy to escape the atoms. So there is always a "conduction band" overlap and an electron excited enough can always go anywhere (you only need to heat things up enough). And of course, energy comes in quantum so the conduction space is not actually continual but discrete, but it's possibly not important here. At least that's how I understand it, which also may or may not be correct. :)
Thanks for the awesome animation and explanation! Wouldn't you say that the electrons that lose energy and recombine actually make up the depletion region? In your animation, the depletion region increases but the electrons in the valence band remain outside of it. Thanks for your answer!
Hello, I'm a bit confused by the animation. when the free electrons go over to the p-site, you would think that the result would be a neutral charged atom at the N-site, but instead it becomes a positive charged hole?
Sir, thank you so much for making this video. It is extremely helpful and easy to understand! The textbook made me wish I would rather have my brains blown off😅😄😄😄
Hi, thanks for the interesting and instructive video, but one thing I don't understand is why we can't disconnect these semiconductors from each other. Thank you!!
Thanks for the question! Do you mean, why we have to have the two different doping regions? If you have just a p-doped region or an n-doped region by themselves, they're just a piece of material that doesn't conduct particularly well. It's when they're put together that the magic (or science) really happens! If you're not familiar with the background on doping, I recommend starting at the beginning of our Semiconductor Basics playlist: th-cam.com/play/PLfYdTiQCV_p7sDswtLZKK43BWOd2mTmHC.html
@@CircuitBread Thank you for the answer, I will definitely start watching. I worded my question incorrectly. I just can't understand the Seebeck effect. How does it happen?
Sir! As electron is negatively charged and hole is positively charged then after the electron get into hole how can there be negative charge left????? Sir please answer
So the depletion is essentially the degradation of the materials? Am i getting that right. Because it's electrons become excited and flow out of the material when the voltage is applied though heat (sunlight) I'm talking about solar panels here, but the concept remains the same through diodes. LEDs last a super long time because the material is so much better at limiting the amount of electrons that can flow out of the depletion area in the form of light photons. Semiconductors are cool 🤓. From this video I have learned that an LED is basically the reverse of a solar panel
nice video but at 1:11 electorns filling the holes shown as they stay as negative charges. As I read in a book , they neurtalize each other and some majority carriers holes and electrons are lost in this process. How negative charges exist in is because holes leave behind electrons when they diffuse throught, similar to electrons leaving out holes behind them.
Yep, you're exactly right - those electrons combine with the holes and while the electrons still technically exist, they're no longer important to consider as they're now tightly bound to a nucleus and there is no net charge. This is the tradeoff in trying to show a process visually that can't truly be shown visually in a realistic manner. If we'd made the hole and electron disappear, that could have been confusing in that people would have thought the electron literally disappeared, when it's really just the charges are canceling each other out. So we had to make a decision on how we thought it best to represent it. But it sounds to me like you have a great understanding of the topic, which is great!
Why dont the electrons in the n-type move into their the depletion zone from their side ? they have a sea of positive charges to the left and a sea of negative charges to the right. I get why they dont cross they boundary this makes sense to require some energy , but why dont they just move into the depletion zone. I understand that there is an electrostatic field that points to the left but i dont understand why this works out when i imagine an electron that is near the edge of the depletion region from the right , naturally the forces would push it into the depletion region
Wow. This was so helpful. I wish you'd make a video on the applications of pn junction especial rectifiers Your videos just make it so much easier to understand ❤
We do have a couple videos on diodes (which is just a PN junction) and I've been thinking about perhaps doing a small sub-series as part of our Circuits 101 series about the applications of BJTs (which are NPN or PNP junctions).Thanks for the feedback!
I had a question: At the pn junction where there is a layer of +ve and -ve charge opposite each other how is a region of DEPLETED charge carriers created, surely there is a concentration of charge carriers?
The trick here is to realize that those charges are immobile ions, not free moving charge carriers (something that is inaccurate in one of our animations, unfortunately). Does that help understanding this?
you forgot to mention that the holes from the p type semiconductor diffuse to the N type semiconductor the same mechanism as the electrons diffuse towards the p type semiconductor. but overall video is amazing, thank you.
Why when the depletion area expands, the energy level of conduction and valence decreases in n region, "energy level or energy band of solid should be constant"
Hi Roshan, my understanding is that the electron loses that energy in the process of overcoming the depletion region, which is acting as a barrier. In other words, it uses that energy just in the process of getting to the other side.
Can you kindly explain the reason why p side energy levels are made higher and in n-side they are made lower. Also why in the state of equilibrium holes and electron Fermi level align at same position in order to achieve equilibrium. Also as holes and electron which flow are actually in bond with the atom, so hows does when they are in contact, what provides them energy that electrons move and fill the vacant charges in p side leaving a hole or vacant side in n side.. In many texts i have seen (but still confused) that they say, electron are near conduction band so as electron moves they actually decreases the amount of Fermi level in n side due to vacancy and increases the Fermi level o p side... but the logic that Fermi level will align finally for both p and n side, i am unsatisfied with it...Some says as depletion region is formed so why further movement of electron and holes do not occur that electron may go to conduction band of p region. Sorry a bit long query and may be dumb question, but please do clarify this and hope you reply to me. Also you said that electron coming from n type to p type during diffusion will fall back to valance band of p region. How can you represent this situation in a pn semiconductor. is it that the electron recombine with the immobile ion created in p region or what.
so a diode allows current to pass through when activated Like a gate. so why wouldnt use a mosfat instead because a mosfat also allows current to go through when activated.
after pentavalent doping the extra electrons goes in conduction band of that semiconductor am i correct? i understood everything and clear my doubts thanks!
"the trivalent atom has lower force in the talk is wrong. the Born nucler core has strong force becuase the out layer electron is more close to the core.
Sir, My Second Question is why does the free electrons rapidly lose energy while falling into the holes right after crossing the p-n junction (at 3:26) (I understand WHY it should, because the acceptor energy level is lower than the valence Band obviously, I just don't know what underlying phenomenon makes the electrons lose energy) And, my 3rd Question is- similarly, what makes the overall energy level of the n region to decrease as soon as a depletion region is created? (at 3:39)
Your second question seems nearly philosophical when I read it. They lose energy because they tend toward the lowest energy level, just like why a marble in a bowl wants to settle in the bottom. And hitting the bottom of the bowl causes the marble to jump up, just like the insertion of energy (in terms of heat or light) causes the electrons to jump out of the valence band. Any underlying "why" below that... I don't know! Let's see if I can do an adequate job explaining the third question. Even though the overall semiconductor has the same energy, the energy has been redistributed by the movement of electrons and holes within the semiconductor. As the n region is dropping in energy, the p region is increasing in energy, so that's where you get the balancing. And it isn't decreasing as soon as the depletion region is created, it's dropping in conjunction with the depletion region being created. The two things are related. Hopefully that clarifies things!
Thank you so much, all your answers are really helpful. But I'm so sorry that I'm having too many questions to bother you again and again, ha ha! Anyways, so what you just said about why electrons lose energy while falling into holes (you said that it's just a natural tendency to have lowest energy) so why does that tendency come visible "after" the electron has crossed the junction? Does it mean that any valence band electron on the n side can just jump down to valence band randomly? If not, then what's making that change of energy drop ONLY after the passing of electrons? (it's fine if you can't give the accurate answer to this, I went pretty deep😅...but if you know any other resource as suggestion where I can find the best but easy explanation, that would be a great bonus favor, too) For your response to the 3rd question (energy gradient increment between n and p regions with depletion layer formation): I do want to ask that referring to one point you made in the video about why initially the energy levels of n type semiconductor is naturally a bit less than p type. There you had explained the reason in terms of effect by nuclear attractions. So my question is, if we consider the energy drop / energy jump in the respective n and p regions during the depletion layer is being formed, how can that be explained in terms of thr nuclear attractions (individually for n type and p type)?
@@aryanandaleebazim823 No problem! My only concern is that we're getting close to the edge of my understanding -and I'd prefer to have Dr. Campbell help (a professor and awesome person that we've used as a resource to double-check our work in microelectronics) but she's always crazy busy. So I will do my best! I think we need to expand the bowl analogy more. In reality, it's not just one bowl, it's trillions and quadrillions of bowls per square centimeter of lattice. And even though that may sound like a lot, it's absolutely tiny compared to the amount of atoms in that same area. So, at this point it becomes a statistical thing. But the more bowls there are, the more likely that an electron will find one and then fall into it to the lower energy level. Once the electrons cross through the depletion region, there are a lot more bowls, so it's statistically much more likely that the electrons will drop down in energy level at that point. If I'm understanding this question properly (which I may not be) you're trying to figure out why the n and p regions have an even greater difference in energy levels due to the nuclear forces on trivalent versus pentavalent electrons, AFTER the depletion has been formed. I think, in this case, that this is not actually the case. This change after the formation of the depletion layer is not due to the nuclear forces between the nucleus and the valence electrons but simply by the energy of the extra electrons that are moving from the n region to the p region. So, instead of the inherent differences in energy levels due to the nuclear forces between the nuclei and electrons, it's due to the physical movement of particles that have intrinsic energy. Does that make sense? I'm not sure if I could go any deeper than that without getting a degree in chemistry or physics. 😀
Wont the electron leave a hole behind beacuse the electron from the n region migrate to p region So wont the donor atoms have a hole since it donated one of its electron?
Good question and one that I wish we had explicitly answered when we made this (hindsight is 20/20). Basically, yes, it will leave a hole behind UNLESS the donor atom had an extra electron in the area any (such as a five electron material as part of a four electron substrate). But, since it's a circuit and the electrons are flowing around the loop, that hole gets filled as the electrons come around. So we aren't accumulating holes on that side because they're actively being filled up as well. I hope that helps!
I think it's because the opposite is true for pentavalent atoms compared to trivalent atoms. Pentavalent atoms exert much more force on the outermost electrons, causing the orbits of the outermost electrons to be much lower and nearer to the source. Hence the bands in n type are located at a lower energy level compared to the bands in p type.
@@justinsantos5751 I think so, too! my professor said that "The bigger, pentavalent atoms are "attracting" their outermost electrons more, so their energies are lower, meaning, further from the 0, i.e. the vacuum level."
@@CircuitBread mmmm so electron only occurs in conduction band when we put energy into it. But in this case, p-n junction is in equilibrium state(no external energy include). Which makes me wonder how does an electron occurs in an conduction band when we didn’t put energy into a system😋
There are electrons in the conduction band at almost all times, there just aren't usually enough to do much of anything interesting. The numbers we're dealing with are absolutely enormous - literally mind boggling. But, in addition to that, for n-type doping, you're introducing more electrons to the system, which further increases the amount of electrons in the conduction band - even when it's not biased (when there's no external energy included). I hope that helps!
For me. It still doesn't make sense like If atom is in static position. And the only thing actually moving is electron. What will this looks like??? Are there any simulation like this?
One of the challenges with showing these things visually is that everything is just representational. It would be awesome to show it how it actually is but 1) it's hard to show something where you're dealing with literally trillions of atoms and 2) it gets even messier in 3D and 3) in this case, it wouldn't actually demonstrate the concept we're trying to show off here. For the band gap, there isn't a literal physical gap, it's a gap in the energy levels that the electrons can possess. It's sort of like saying that an electron can have an energy level of 1 and 2, but then the next level it can have is 5. So the gap is energy levels 3 and 4. And while this seems strange at first, remember that in chemistry we learned the different energy states of electrons for individual atoms. This is just expanding on that. Sadly, this explanation isn't entirely accurate either but will hopefully help establish a conceptual understanding that can be expanded on.
Although it's a 5 mins video but it explains a lot and what I mean by a lot doesn't just means "a lot" but it means A LOT! Thanks for the Exceptional work, and keep nourishing our minds with that great way of putting up science
1:06 1:13
I like your profile pic xD
Searching for animation and till now, this is the best available video on TH-cam
Glad you liked it
Are u from fbise?
As a material and nano tech engineer it helped a lot thank you so much! This 5 min video was definitely more effective than the 2 hours lesson I took at uni
The question is why do course staff, who are paid for the job, fail to explain this concept as clearly and simply as this TH-cam channel does!
Thank you for the video!
init
true true
on the course teachers' defense, they rly cannot explain the topics with the help of such intuitive animations shown in youtube videos
but still overall I feel youtube just does a better job at teaching us lol
You probably gave no indication that you didn't understand the material. It's adult learning, so if you don't get the most out of what you are paying for then that's on you. Secondly, there is a bit of confirmation bias in your statement. You have obviously received several hours of face to face tuition and have tried to read your course material in your own time, yet you give 100% of the credit to this video only? Do you think you would have understood everything about diodes if you had just watched this once?
@@TheEsky18 so true
We hope this video was helpful! We have a couple more videos on how diodes/PN junctions work when forward and reverse biased, we recommend you go check them out as well. We also have a wide variety of other tutorials on semiconductors, so explore our channel if you have any more questions on this topic. If helpful, we have the transcript for this video on our website here: www.circuitbread.com/tutorials/how-does-a-diode-work-part-1-the-pn-junction Take care!
Sir, the depletion region consist of electrons of n region toward p side and holes of p region towards n side
after watching many videos, this series on transistor fundamentals is the best so far. The animation is clear and the speaker makes perfect sense. Subscribed.
This is the type of content that viewers seek from youtubers. Quality Content!!
I love this channel. Every time I feel my brain frying while studying I come here and understand it within minutes. Just excellent.
Thanks for making the concept so clear and elegant your way of teaching is really impressive and far reaching
it is simply perfect I was reading slide almost 40 mins but couldn't understand anything about concept until watch this 5 minutes video.Thank you
Glad it helped!
This is the COMPLETE explanation.
Perfect. Good job!
This was so helpful. I have my physics full syllabus grade 12 exam tomorrow and God semiconductors were one of the most confusing chapters...That is until I watched your videos
Thank you so much. The concept is crystal clear
thank you. this animation helped me understand what my teacher couldn't through a powerpoint slide
This is so far the best explanation for PN Junction for me
Awesome, great to hear!
Using the band diagram to explain the equilibrium state is very impressive in regard to the traditional built-in potential explanation.
amazing explanation that I've ever seen before. irreproachable scientific content. Well done!
This series is amazing. I have been looking for a good source to learn about electronics and I've found it, without a doubt.
Thank you for this clear explanation. Nam professor nim kaalu kelage thurbeku.
I love the way you explain and animation, it's very easy to understand
This was by far the most intuitive explanation of band diagram of pn junction I have seen. Thanks brother.
Just a minor nit pick in the animation
It would have been more clearer to specify that movable charge carriers cross the pn junction and ionize the fixed carriers on the other side
So the depletion region is filled with ionize fixed carriers but you showed that carriers were moving during the formation of depletion region, which I guess shouldn't happen in reality
But regardless this was a fantastic video thanks
Great explanation! Thank You so much!!! Love from Brazil!
Take love from Bangladesh 🇧🇩
even the concept which i didnt even had an idea in one hour explanation, i understood here after 5 minutes
Thx sir, i would search across the internet for an easy explanation but for an 1h i could only find YOU
Finallly you helped me understanding this topic. Really thank you! Other websites make it so difficult.
You're welcome, I'm glad it helped!
Wow brilliant, thanks for this fantastic video, first time I actually understand how diodes actually work!
Awesome!
the best explanation, was looking for it for some time
The best explanation for pn junction diode. Hey everyone, I wanted to praise CircuitBread for creating an incredibly helpful video. The content was so informative and well-explained. I'm sure it helped many others as well. Thank you for taking the time to share your knowledge and expertise!.
Thanks. Glad it helped!
The best video I find about diodes and pn junction. Learned a lot ❤️
beautiful English subtitle and animation video, thank you so much teacher .From Viet Nam with love
Its awesome.love from lahore ,pakistan.you are included in my list of best teachers.❤
this video is heavily underrated
Thank you for these lectures, it is great to have multiple sources of information, but it is still a confusing topic.
so why aren't those negative charges (electrons) change places with positively charged... what exactly? Ions? holse?
First, let me thank you for the good videos. But in this one, I wonder if it's factually correct. What I have in mind specifically is the energy diagrams at 2:30. There is not enough space to explain in detail but in a nutshell: the valence band of the p-region can be above or below of valence band of the n-region, depending on used materials. Take for example P atom with electron configuration [Ne]3s^2 3p^2 => 5 electrons with principal quantum number = 3 vs B atom (you named it as p-type impurity) with [He] 2s^2 2p^1 => 3 electrons with PQN=2. So electrons in the B valence shell have even lower energy than those in P. Ga or In atoms would work (see periodic table).
Second and more importantly - when elections recombine on PN junctions the electron energy needed to escape from P atom DOES NOT change. Bands are not moving anywhere contrary to your statement in 3:41. These are still the same atoms. P atoms further in the n-region are willing to give up the extra electron same as before. These may either recombine with holes in the p-region closer to the PN junction (causing hole current) or may try to penetrate to n-region and recombine with the n-region hole.
The only problem is really that there is already a barrier of earlier recombined negative ions of B/Ga/In atoms. These exert a repelling force on free electrons coming from the n-region according to Culomb's law (as you correctly explain in 2:00).
In a nutshell to understand PN junction it's critical to understand 2 distinct forces - 1) Culomb's law and 2) the proclivity of electrons to fill the atom valence shell in some patterns which is key for understanding chemical bondings, the periodic table, and chemical element properties.
Also, I think there is no conduction band but rather conduction space simply for all electrons with enough energy to escape the atoms. So there is always a "conduction band" overlap and an electron excited enough can always go anywhere (you only need to heat things up enough). And of course, energy comes in quantum so the conduction space is not actually continual but discrete, but it's possibly not important here.
At least that's how I understand it, which also may or may not be correct. :)
Excellent. Clear and concise. Thank you.
thank you for this animation. drifting of the positive charge from p to n junction has not been shown does it not occur explain please
Thanks for the awesome animation and explanation! Wouldn't you say that the electrons that lose energy and recombine actually make up the depletion region? In your animation, the depletion region increases but the electrons in the valence band remain outside of it. Thanks for your answer!
my uni cant explain this at all, have to come to your vids to properly understand it. Thanks
Happy to help!
Thanks. Love from India
Why i didn't find this video earlier
U r doing great wrk
I appreciate it too much
Thanks for your feedback, we really appreciate it!
Hello, I'm a bit confused by the animation. when the free electrons go over to the p-site, you would think that the result would be a neutral charged atom at the N-site, but instead it becomes a positive charged hole?
I guess it is because it are mostly neutral molecules from the n-site that will lose an electron?
Thankkss really
I have exam after 1 hour
I read it in abook school
I understood superficially, but I didn't really understand exactly how it happened
Sir, thank you so much for making this video. It is extremely helpful and easy to understand! The textbook made me wish I would rather have my brains blown off😅😄😄😄
Well, I'm glad you didn't and that this helped!
Great video, explain a profound theory in a simple language
Extra ordinary content. Thank you very much for sharing.
High quality content 👍🏼
Excellent video and easy tounderstand, well done 👏
Out of all the videos I’ve seen , this is by far the best ! Thank you so much sir 👍🏻
8076291502
It was helpful basic electronics tutorial I even seen
Thanks so much for the feedback!! Check out our site CircuitBread.com for all of our tutorials plus tools, an equation library, and more! 😎
Such a amazing video 😍 helpful
Hi, thanks for the interesting and instructive video, but one thing I don't understand is why we can't disconnect these semiconductors from each other.
Thank you!!
Thanks for the question! Do you mean, why we have to have the two different doping regions? If you have just a p-doped region or an n-doped region by themselves, they're just a piece of material that doesn't conduct particularly well. It's when they're put together that the magic (or science) really happens! If you're not familiar with the background on doping, I recommend starting at the beginning of our Semiconductor Basics playlist: th-cam.com/play/PLfYdTiQCV_p7sDswtLZKK43BWOd2mTmHC.html
@@CircuitBread Thank you for the answer, I will definitely start watching.
I worded my question incorrectly.
I just can't understand the Seebeck effect.
How does it happen?
Sir! As electron is negatively charged and hole is positively charged then after the electron get into hole how can there be negative charge left????? Sir please answer
super helpful thank you so much!!
Why the energy of conduction band and valance band in n type semiconductor is slightly lower than those in p type conductor
So the depletion is essentially the degradation of the materials? Am i getting that right. Because it's electrons become excited and flow out of the material when the voltage is applied though heat (sunlight)
I'm talking about solar panels here, but the concept remains the same through diodes. LEDs last a super long time because the material is so much better at limiting the amount of electrons that can flow out of the depletion area in the form of light photons.
Semiconductors are cool 🤓. From this video I have learned that an LED is basically the reverse of a solar panel
Why is the Valenzband empty? dont we need to fill lower states with electrons first ?
nice video but at 1:11 electorns filling the holes shown as they stay as negative charges. As I read in a book , they neurtalize each other and some majority carriers holes and electrons are lost in this process. How negative charges exist in is because holes leave behind electrons when they diffuse throught, similar to electrons leaving out holes behind them.
Yep, you're exactly right - those electrons combine with the holes and while the electrons still technically exist, they're no longer important to consider as they're now tightly bound to a nucleus and there is no net charge. This is the tradeoff in trying to show a process visually that can't truly be shown visually in a realistic manner. If we'd made the hole and electron disappear, that could have been confusing in that people would have thought the electron literally disappeared, when it's really just the charges are canceling each other out. So we had to make a decision on how we thought it best to represent it. But it sounds to me like you have a great understanding of the topic, which is great!
@@CircuitBread thank you for the reply and also great videos !
waiting for the bread to pop out !!
Great understandable explanation❤
Finally understandable english!
Why dont the electrons in the n-type move into their the depletion zone from their side ? they have a sea of positive charges to the left and a sea of negative charges to the right. I get why they dont cross they boundary this makes sense to require some energy , but why dont they just move into the depletion zone. I understand that there is an electrostatic field that points to the left but i dont understand why this works out when i imagine an electron that is near the edge of the depletion region from the right , naturally the forces would push it into the depletion region
great explanation
GREAT EXPLANATION
Thanks so much man
yes ,he is an inspiration for me ...thank you
Wow. This was so helpful. I wish you'd make a video on the applications of pn junction especial rectifiers
Your videos just make it so much easier to understand ❤
We do have a couple videos on diodes (which is just a PN junction) and I've been thinking about perhaps doing a small sub-series as part of our Circuits 101 series about the applications of BJTs (which are NPN or PNP junctions).Thanks for the feedback!
Sir I did not get the points 2:43 can you explain for me ?
I had a question: At the pn junction where there is a layer of +ve and -ve charge opposite each other how is a region of DEPLETED charge carriers created, surely there is a concentration of charge carriers?
The trick here is to realize that those charges are immobile ions, not free moving charge carriers (something that is inaccurate in one of our animations, unfortunately). Does that help understanding this?
@@CircuitBread Yes, it does, thank you, as I understand the depletion region acts as the 'barrier' in diodes.
Does active region and depletion region are same in LED? IF no what is the difference please explain
superb explanation
Thanks!
Great explanation, thanks for helping me to envisage it.
this is so helpful! thank God I found it haha more videos to come :)
you forgot to mention that the holes from the p type semiconductor diffuse to the N type semiconductor the same mechanism as the electrons diffuse towards the p type semiconductor.
but overall video is amazing, thank you.
Very true, thanks for the feedback!
i have a question what is thee theory about reduce depletion width
Very informative , thank you.
Why when the depletion area expands, the energy level of conduction and valence decreases in n region, "energy level or energy band of solid should be constant"
great explanation! thank you
Nice work,,. Btw The free electrons diffusing through the depletion region from n region rapidly lose energy...
What makes them lose energy ?
Hi Roshan, my understanding is that the electron loses that energy in the process of overcoming the depletion region, which is acting as a barrier. In other words, it uses that energy just in the process of getting to the other side.
Depletion layer has No charge then why u asign it by + & - charge
sir, Could you expain why PN is called minority device? And how MCLT affect device. Thanks a lot~
Pls put video for n type solar cell working
Can you kindly explain the reason why p side energy levels are made higher and in n-side they are made lower. Also why in the state of equilibrium holes and electron Fermi level align at same position in order to achieve equilibrium. Also as holes and electron which flow are actually in bond with the atom, so hows does when they are in contact, what provides them energy that electrons move and fill the vacant charges in p side leaving a hole or vacant side in n side.. In many texts i have seen (but still confused) that they say, electron are near conduction band so as electron moves they actually decreases the amount of Fermi level in n side due to vacancy and increases the Fermi level o p side... but the logic that Fermi level will align finally for both p and n side, i am unsatisfied with it...Some says as depletion region is formed so why further movement of electron and holes do not occur that electron may go to conduction band of p region. Sorry a bit long query and may be dumb question, but please do clarify this and hope you reply to me. Also you said that electron coming from n type to p type during diffusion will fall back to valance band of p region. How can you represent this situation in a pn semiconductor. is it that the electron recombine with the immobile ion created in p region or what.
so a diode allows current to pass through when activated Like a gate. so why wouldnt use a mosfat instead because a mosfat also allows current to go through when activated.
after pentavalent doping the extra electrons goes in conduction band of that semiconductor am i correct?
i understood everything and clear my doubts thanks!
Yep! Excellent to hear. We do have some other tutorials on doping if necessary but it sounds like you're good to go!
والله ودي اجيك البيت اسلمك اللايك شخصيا 🤍
Great explanation....really !!!
How does the depletion layer get charge ?when n and p recombine,will there be charge
Amazing channel :) thank u so much.
"the trivalent atom has lower force in the talk is wrong. the Born nucler core has strong force becuase the out layer electron is more close to the core.
can you explain reverse recovery some time
Sir, My Second Question is why does the free electrons rapidly lose energy while falling into the holes right after crossing the p-n junction (at 3:26) (I understand WHY it should, because the acceptor energy level is lower than the valence Band obviously, I just don't know what underlying phenomenon makes the electrons lose energy)
And, my 3rd Question is- similarly, what makes the overall energy level of the n region to decrease as soon as a depletion region is created? (at 3:39)
Your second question seems nearly philosophical when I read it. They lose energy because they tend toward the lowest energy level, just like why a marble in a bowl wants to settle in the bottom. And hitting the bottom of the bowl causes the marble to jump up, just like the insertion of energy (in terms of heat or light) causes the electrons to jump out of the valence band. Any underlying "why" below that... I don't know!
Let's see if I can do an adequate job explaining the third question. Even though the overall semiconductor has the same energy, the energy has been redistributed by the movement of electrons and holes within the semiconductor. As the n region is dropping in energy, the p region is increasing in energy, so that's where you get the balancing. And it isn't decreasing as soon as the depletion region is created, it's dropping in conjunction with the depletion region being created. The two things are related. Hopefully that clarifies things!
Thank you so much, all your answers are really helpful. But I'm so sorry that I'm having too many questions to bother you again and again, ha ha!
Anyways, so what you just said about why electrons lose energy while falling into holes (you said that it's just a natural tendency to
have lowest energy) so why does that tendency come visible "after" the electron has crossed the junction? Does it mean that any valence band electron on the n side can just jump down to valence band randomly? If not, then what's making that change of energy drop ONLY after the passing of electrons? (it's fine if you can't give the accurate answer to this, I went pretty deep😅...but if you know any other resource as suggestion where I can find the best but easy explanation, that would be a great bonus favor, too)
For your response to the 3rd question (energy gradient increment between n and p regions with depletion layer formation): I do want to ask that referring to one point you made in the video about why initially the energy levels of n type semiconductor is naturally a bit less than p type. There you had explained the reason in terms of effect by nuclear attractions. So my question is, if we consider the energy drop / energy jump in the respective n and p regions during the depletion layer is being formed, how can that be explained in terms of thr nuclear attractions (individually for n type and p type)?
@@aryanandaleebazim823 No problem! My only concern is that we're getting close to the edge of my understanding -and I'd prefer to have Dr. Campbell help (a professor and awesome person that we've used as a resource to double-check our work in microelectronics) but she's always crazy busy. So I will do my best!
I think we need to expand the bowl analogy more. In reality, it's not just one bowl, it's trillions and quadrillions of bowls per square centimeter of lattice. And even though that may sound like a lot, it's absolutely tiny compared to the amount of atoms in that same area. So, at this point it becomes a statistical thing. But the more bowls there are, the more likely that an electron will find one and then fall into it to the lower energy level. Once the electrons cross through the depletion region, there are a lot more bowls, so it's statistically much more likely that the electrons will drop down in energy level at that point.
If I'm understanding this question properly (which I may not be) you're trying to figure out why the n and p regions have an even greater difference in energy levels due to the nuclear forces on trivalent versus pentavalent electrons, AFTER the depletion has been formed. I think, in this case, that this is not actually the case. This change after the formation of the depletion layer is not due to the nuclear forces between the nucleus and the valence electrons but simply by the energy of the extra electrons that are moving from the n region to the p region. So, instead of the inherent differences in energy levels due to the nuclear forces between the nuclei and electrons, it's due to the physical movement of particles that have intrinsic energy. Does that make sense? I'm not sure if I could go any deeper than that without getting a degree in chemistry or physics. 😀
Wont the electron leave a hole behind beacuse the electron from the n region migrate to p region
So wont the donor atoms have a hole since it donated one of its electron?
Good question and one that I wish we had explicitly answered when we made this (hindsight is 20/20). Basically, yes, it will leave a hole behind UNLESS the donor atom had an extra electron in the area any (such as a five electron material as part of a four electron substrate). But, since it's a circuit and the electrons are flowing around the loop, that hole gets filled as the electrons come around. So we aren't accumulating holes on that side because they're actively being filled up as well. I hope that helps!
Thanks a lot ✅
this is gold
Why electron lose energy after moving to the conduction band of p junction and fall to the Valence band of p junction
2:28 Why n-type bands are lower than the p-type bands?
I think it's because the opposite is true for pentavalent atoms compared to trivalent atoms. Pentavalent atoms exert much more force on the outermost electrons, causing the orbits of the outermost electrons to be much lower and nearer to the source. Hence the bands in n type are located at a lower energy level compared to the bands in p type.
@@justinsantos5751 I think so, too! my professor said that "The bigger, pentavalent atoms are "attracting" their outermost electrons more, so their energies are lower, meaning, further from the 0, i.e. the vacuum level."
If Conduction band has electron when we put an energy into it. Why does the conduction band of p-n junction has electron? Thank you in advance!
I'm sorry, I don't really understand the question...
@@CircuitBread mmmm so electron only occurs in conduction band when we put energy into it. But in this case, p-n junction is in equilibrium state(no external energy include). Which makes me wonder how does an electron occurs in an conduction band when we didn’t put energy into a system😋
There are electrons in the conduction band at almost all times, there just aren't usually enough to do much of anything interesting. The numbers we're dealing with are absolutely enormous - literally mind boggling. But, in addition to that, for n-type doping, you're introducing more electrons to the system, which further increases the amount of electrons in the conduction band - even when it's not biased (when there's no external energy included). I hope that helps!
@@CircuitBread thank you so much!
For me. It still doesn't make sense like If atom is in static position. And the only thing actually moving is electron. What will this looks like??? Are there any simulation like this?
One of the challenges with showing these things visually is that everything is just representational. It would be awesome to show it how it actually is but 1) it's hard to show something where you're dealing with literally trillions of atoms and 2) it gets even messier in 3D and 3) in this case, it wouldn't actually demonstrate the concept we're trying to show off here. For the band gap, there isn't a literal physical gap, it's a gap in the energy levels that the electrons can possess. It's sort of like saying that an electron can have an energy level of 1 and 2, but then the next level it can have is 5. So the gap is energy levels 3 and 4. And while this seems strange at first, remember that in chemistry we learned the different energy states of electrons for individual atoms. This is just expanding on that. Sadly, this explanation isn't entirely accurate either but will hopefully help establish a conceptual understanding that can be expanded on.
Great video thank you
too dope too good well done .