@@proudnepali8388 bro actually holes are vacant spaces as you said only the electrons will be crossing the barrier but not the holes . Holes in p type are present in the valence band of p type wheras electrons in n type are in conduction band so to reach the valence band of p type they have to first reach conduction band of p type which has very few electrons(which are minority carriers of p type) and then loose energy to goto valence band to fill the vacant spaces.
Actually holes are not moving....it seems that they are moving since electron are moving....holes seems to move in a direction opposite to electron. Remember:I am using word 'seems'.
Whenever I get a problem all I search for is these videos..these are great. And his teaching method is superb. We can feel that friendliness in his voice. Love it❤
You are by far the best animator. I can actually believe and visualize what is written in the book because of you. Please keep making many more videos:) You really helped me out!
one of the best videos i have ever seen out there. so simply explained with the right gear, everything is perfect about it and super easy to understand
In addition to ur extraordinary teaching of physics.....ur vocabulary is excellent as well. Like "All hell breaks loose " "Diffusion current sky rocket's " Plz teach us English too .....ur amazing sir
Best bestttttt🔥🔥🔥🔥🔥💞💞💞💞💞💞 I finished my 12th class with dissatisfaction of this chapter,bcz it’s concept wasn’t clear for me. Now after long time im seeing this and feeling so happy and having content, i cant describe 💜
Great work khan academy though i am preparing for GATE i had confusion before seeing your videos and nobody else other than you explained it in crisp and crystal clear way ....keep this good work continued
I have a question If in forward biasing the electrons flow from n type to p type region Then shouldn't the depletion region increase. And electron may recombine again with holes, like they did when the depletion region was initially formed
There is constant potential is applied right then there is chance of recombination as the electrons were keep on feeding by potential thus no recombination I think in this way😊
sir, your way of teaching is so great,pls clarify my doubt/ when ext electric field is applied from p to n type then diffusion current increases,that doesnt destroy the charge carriers and increases internal electric field from n to p type which further increses the barrier width?
Sir, I have a confusion in this concept for many years. Could you please solve my doubt ? 4:31 If the barrier voltage is 0.7 volts and you are applying 0.2 volts in forward bias, there is still 0.7 - 0.2 = 0.5 volts of barrier potential. Then how does the current flow ?
I am not sure if i understood it right but i think when the value was 0.7 only a few of em could go across the depletion region but when it was reduced to 0.5 and also at the same time made the region smaller, it basically made it possible for some more of the holes (which could've crossed with lesser energy) to go accross the depletion region and vice versa for the electrons. Hence as it isn't under equilibrium anymore, current flows.
bro actually holes are vacant spaces as you said only the electrons will be crossing the barrier but not the holes . Holes in p type are present in the valence band of p type wheras electrons in n type are in conduction band so to reach the valence band of p type they have to first reach conduction band of p type which has very few electrons(which are minority carriers of p type) and then loose energy to goto valence band to fill the vacant spaces.
This guy casted a magical spell on me cause I got this topic crystal clear. (Matter of shame:)👇👇👇👇👇 ( I learnt this in school with my teacher and even attended a video lecture for an hour on youtube but still I wasn't convinced.)
Why is the diffusion current increasing when you apply a forward bias ? Drift currents means that the motion of charges is due to an electric field while Diffusion is caused by difference in concentration. When you apply a forward bias you create an applied electric field across the junction that will make the carries DRIFT to the opposite side not DIFFUSE.
You can think in this way that, When we are appling the Forward biasing then the majority charge carriers (Let say holes of the P Region ) are facing the repulsion from the holes that are coming from the battery (As it is Forward Biased), Knowing the fact that battery also emitts nothing but the free charge carriers. So due to this majority carriers start pushing in the forward direction and hence the current due to majority charge carriers in forward direction increases (So called as diffusion current). Drift current is due to minority charge carriers (These carriers are the ones that are present before the doping when the semiconductor was so called INTRINSIC Semiconductor, In which both the electrons and holes are present in equal concentration and the doping came which increased the concentration of one type of charge carrier and made another one a minority charge carrier.), So if we are appling forward biased then these will oppose but their oppose is very little as compared to majority charge carriers (As their concentration is also low). Hope this helps. :)
This video is great to conceptualise the PN junction mechanism.. i have just one doubt.. plz clarify it.. as u earlier said in previous videos, diffusion would expose the charged ions B- and P+ so with time drift motion increases due to minority charge carriers due to depletion region?? Isn't it?? Or is it just about the dominating factor? That here depletion region goes down inturn increasing diffusion current rather than contributing to drift motion?
Hello sir, what happens to the electrons after they migrate towards the P side? Do they recombine with the holes, and does the pair get destroyed? If so, wont amount of charge carriers go down with time? Thanks already!
@@KhanAcademyIndiaEnglish Khan Academy India - English Thank you for replying sir! I just watched that video, and it was truly helpful. Really glad that I understand how it works now! Just one more doubt sir, Given enough time, will the diode run out of majority free charges in reverse bias as the depletion region keeps on growing?
I should ask this cuz this question is really irritating me. If the diffusion increases in the forward-biased PN junction shouldn't there be more exposed ions and shouldn't the width of the depletion region increase?
Your notes available? If available where to find them...reallly besttt teacher ever now a month left to my exams, no time to write lecutres as I've 3 days to prepare I wish O had find them before😢😢😢😢
Electrostatics and circuits belong to one science not two. For a unified approach to learning Current and the process of conduction watch these two videos i. ua-cam.com/video/REsWdd76qxc/v-deo.html and ii. ua-cam.com/video/8BQM_xw2Rfo/v-deo.html Also, in the textbooks referred in the last frame of video i you will find descriptions of the operation of resistors, capacitors and inductors using this approach which makes it easier to understand. There are also chapters in the textbook references which explain the operation of diodes and transistors using the unified approach and includes descriptions of forward and reverse biasing p-n junctions.
Q. True or False: In a pn junction diod without any external potential source, the diffusion current and drift current are caused at the junction by- 1. Majority carriers for diffusion current 2. Minority carriers for drift current 3. No current at the junction
Sir while Forward Biasing a PN Junction, there will be current flowing in both directions, right? Because both diffusion (major) and drift (minor) are happening. So there will be a tiny current flowing from N to P. So we can't use this Forward Biased PN Junction in daily life (as the main goal is to allow current to flow only in one direction)
In forward bias, the diffusion current is orders of magnitude larger than drift, so there is a high current from P to N. In reverse bias, there is a very tiny drift current from N to P. In most applications this is negligible Thus the diode acts as a one-way switch, conducts in the forward bias, but doesn't conduct (negligible conduction) in the reverse bias. Hope this clarifies your doubt.
If the electrons are moving from battery to n region and filling the holes in p type region then why the flow of electrons/electricity is opposite in simulation?
Good question. Let's think about electrons. Towards N side terminals there are loads of free electrons (as most holes don't make it there). Think of this terminal as the source of electrons. Now as these electrons diffuse into P side they keep recombining. The lost electrons are replenished from that 'source'. Okay so won't that 'source' eventually run out of electrons? No. For every electron that moves out of it, it pulls an electron from the wire immediately next to it. That's how electrons move in the wire as well. Let me know if this helps.
How does increase in diffusion current decrease the depletion layer? It doesn't make any sense coz diffusion caused depletion layer.. plz do reply this question..
The depletion layer decreases due to the external power voltage supplied. This inturn increases diffusion because the depletion region was acting as a barrier for diffusion.
Hi! I just want to ask why the voltages in the neutral zones don't change when a forward bias is applied? Since we know that when voltage is applied to any component, there will be an electric field inside it which points from positive to negative, and since the diode originally has no electric field in its neutral zone to cancel it, shouldn't there be a voltage in the neutral zones? Is there some kind of mechanism that counteracts this?
That's a great question. We are doing a lot of assumptions here, and one of them is the negligible resistance in the neutral regions. This is similar to how we neglect the resistance in wires and assume no electric field there!
@@KhanAcademyIndiaEnglish Please help me‼️‼️‼️ please , how can holes travel to N region , they are just the vacant place where electrons lack right ???
@@proudnepali8388 Hole are the vacant space. Since the negative terminal of the battery is connected with n type semiconductor where electron are the majority charge carrier. And the positive terminal of the battery is connected with P type semiconductor where the hole are the majority charge carrier. Due to the repulsion between negative terminal of the battery and free electron as well as the repulsion between positive terminal of the battery and hole the depletion layer width decreases. So that the some energetic free electron migrates from n type semiconductor to P type semiconductor due to decrease in depletion layer(resistance decreases). Before migration in the n-type semiconductor there was neutral condition but after the Migration of some energetic electron there are generated some hole in the n type semiconducyor. So due to migration of free e there is some hole are generated. That we call migration of hole .
Why don’t the boron and phosphorus atoms just combine chemically and form boron phosphide instead of existing as separate layers just beside each other?? In an atom, the constant motion of electrons and the presence of neutrons altogether prevents the electrons from just collapsing into the positively charged nucleus, what stops boron and phosphorus from chemically combining here??
All the concepts you gave upto this point were great but this video has pretty low standard as far as concept is concerned... you should have talked about flow of electrons rather than saying holes are flowing and should have talked about conventional and electron current
There are two types of electrons. Free electrons that flow freely, and valence electrons (which are covalently bonded) which move from one 'hole' to another. These two motions are pretty independent of each other. The free electrons literally move over some distance. But the valence electrons just jump to a neighbouring hole, virtually moving the hole in the opposite direction. Then the next neighbour will jump in and then the hole again moves (virtually). So you see these valence electrons are not really moving from one place to another (just jump to their neighbouring space and sit there). Hence it makes it both easier mathematically and intuitively to imagine that these 'holes' are moving. This is why we treat holes as a separate individual particle and consider it's motion in the valence energy region (just like how free electrons move in the conduction band region). If you need more details on this, they are explained in previous videos, do check out the playlist. Hopefully, it would help.
@@gold8780 The guy (Mahesh Shanoy) is an indian. From India. It's not fake accent, it's an indian accent. Because he's an indian, from India. Plus you're on a channel called Khan Academy India and you're complaining about an indian accent?
The battery applies an electric field from positive to negative initially since diode is forward biased consider holes as +ve charge carriers for simplification
The best explanation of semiconductors on the whole internet, never understood this concept, but you made it really intuitive, thanks!
Please help me, how can holes travel to N region , they are just the vacant place where electrons lack right ???
@@proudnepali8388 yeah ur right. ig we are assuming the vacant spaces as holes.
@@proudnepali8388a as Xa rqxw
@@proudnepali8388 bro actually holes are vacant spaces as you said only the electrons will be crossing the barrier but not the holes .
Holes in p type are present in the valence band of p type wheras electrons in n type are in conduction band so to reach the valence band of p type they have to first reach conduction band of p type which has very few electrons(which are minority carriers of p type) and then loose energy to goto valence band to fill the vacant spaces.
Actually holes are not moving....it seems that they are moving since electron are moving....holes seems to move in a direction opposite to electron.
Remember:I am using word 'seems'.
Whenever I get a problem all I search for is these videos..these are great. And his teaching method is superb. We can feel that friendliness in his voice. Love it❤
Superb video quality ... This man has put his heart and soul to it
Damn sir .... What a detailed analysis of semiconductor .....Helps for jee preparation !!!!!
You are by far the best animator. I can actually believe and visualize what is written in the book because of you. Please keep making many more videos:)
You really helped me out!
one of the best videos i have ever seen out there. so simply explained with the right gear, everything is perfect about it and super easy to understand
your lecture Answered my lot misconception, you rock the stage!
6 YEARS STILL THE BEST VIDEO EVER
The most productive 6 mins of my day today!
Explanation: top notch
Time: 👍
Beautiful, pure art❤
Made me speechless... Amazing
Wish all teachers should like you
In addition to ur extraordinary teaching of physics.....ur vocabulary is excellent as well.
Like "All hell breaks loose "
"Diffusion current sky rocket's "
Plz teach us English too .....ur amazing sir
Sir why are they not recombining and increasing the depletion region when you are connecting it to a battery.
Thanks a million !!
Best bestttttt🔥🔥🔥🔥🔥💞💞💞💞💞💞
I finished my 12th class with dissatisfaction of this chapter,bcz it’s concept wasn’t clear for me.
Now after long time im seeing this and feeling so happy and having content, i cant describe 💜
Simply brilliant sir❤
it was phenomenal🎉
thankyou verry much for this great explanation
This is a great video. I just wish there were more Khan Academy videos aligned to CBSE curriculum.
I feel you. We are working on it for class 10th currently.
They are kind of connected to the cbse curriculum I guess. I’m a cbse student and many of the topics they have are a part of cbse curriculum
Great work khan academy though i am preparing for GATE i had confusion before seeing your videos and nobody else other than you explained it in crisp and crystal clear way ....keep this good work continued
I have a question
If in forward biasing the electrons flow from n type to p type region
Then shouldn't the depletion region increase.
And electron may recombine again with holes, like they did when the depletion region was initially formed
There is constant potential is applied right then there is chance of recombination as the electrons were keep on feeding by potential thus no recombination I think in this way😊
Just amazing. Thanks sir.
Doesn't the rate of recombination now increase as more holes and electrons are now moving?
I wonder which app he uses for the videos...amazing
Simply Brilliant 👏 👌
Great! It would be also nice to see band diagrams associated to this pictures in the video. Like the ones in previous videos.
sir, your way of teaching is so great,pls clarify my doubt/ when ext electric field is applied from p to n type then diffusion current increases,that doesnt destroy the charge carriers and increases internal electric field from n to p type which further increses the barrier width?
5:58. Sir, is the cut in voltage at forward biasing is equal to the barrier potential of the semiconductor?
that was too good omg
No, you're wrong. This guy could even make ToyStory using this software.
Fr fr
Such a great explanation.
Sir, I have a confusion in this concept for many years. Could you please solve my doubt ?
4:31 If the barrier voltage is 0.7 volts and you are applying 0.2 volts in forward bias, there is still 0.7 - 0.2 = 0.5 volts of barrier potential. Then how does the current flow ?
I am not sure if i understood it right but i think when the value was 0.7 only a few of em could go across the depletion region but when it was reduced to 0.5 and also at the same time made the region smaller, it basically made it possible for some more of the holes (which could've crossed with lesser energy) to go accross the depletion region and vice versa for the electrons. Hence as it isn't under equilibrium anymore, current flows.
Great fun, well explained.
It is very clear explanation
bro actually holes are vacant spaces as you said only the electrons will be crossing the barrier but not the holes .
Holes in p type are present in the valence band of p type wheras electrons in n type are in conduction band so to reach the valence band of p type they have to first reach conduction band of p type which has very few electrons(which are minority carriers of p type) and then loose energy to goto valence band to fill the vacant spaces.
This guy casted a magical spell on me cause I got this topic crystal clear.
(Matter of shame:)👇👇👇👇👇
( I learnt this in school with my teacher and even attended a video lecture for an hour on youtube but still I wasn't convinced.)
Which school?
Please help me, how can holes travel to N region , they are just the vacant place where electrons lack right ???
Bro I guess you r Nepali please help me if you have understood this
Why is the diffusion current increasing when you apply a forward bias ? Drift currents means that the motion of charges is due to an electric field while Diffusion is caused by difference in concentration. When you apply a forward bias you create an applied electric field across the junction that will make the carries DRIFT to the opposite side not DIFFUSE.
You can think in this way that,
When we are appling the Forward biasing then the majority charge carriers (Let say holes of the P Region ) are facing the repulsion from the holes that are coming from the battery (As it is Forward Biased), Knowing the fact that battery also emitts nothing but the free charge carriers. So due to this majority carriers start pushing in the forward direction and hence the current due to majority charge carriers in forward direction increases (So called as diffusion current).
Drift current is due to minority charge carriers (These carriers are the ones that are present before the doping when the semiconductor was so called INTRINSIC Semiconductor, In which both the electrons and holes are present in equal concentration and the doping came which increased the concentration of one type of charge carrier and made another one a minority charge carrier.), So if we are appling forward biased then these will oppose but their oppose is very little as compared to majority charge carriers (As their concentration is also low).
Hope this helps. :)
Man u r really great pls keep uploading more vdos on physics ;)
Thanksss 😊😊
amazingly explained!
This video is great to conceptualise the PN junction mechanism.. i have just one doubt.. plz clarify it.. as u earlier said in previous videos, diffusion would expose the charged ions B- and P+ so with time drift motion increases due to minority charge carriers due to depletion region?? Isn't it?? Or is it just about the dominating factor? That here depletion region goes down inturn increasing diffusion current rather than contributing to drift motion?
Perfect 👏👏
If you want understanding.....physics wallah
If you want depth and clear concept....Khan academy
Hello sir, what happens to the electrons after they migrate towards the P side? Do they recombine with the holes, and does the pair get destroyed? If so, wont amount of charge carriers go down with time? Thanks already!
Great question, I guess this is covered in great detail in the next video titled "Forward & reverse current mechanisms"
@@KhanAcademyIndiaEnglish Khan Academy India - English Thank you for replying sir! I just watched that video, and it was truly helpful. Really glad that I understand how it works now! Just one more doubt sir,
Given enough time, will the diode run out of majority free charges in reverse bias as the depletion region keeps on growing?
I should ask this cuz this question is really irritating me. If the diffusion increases in the forward-biased PN junction shouldn't there be more exposed ions and shouldn't the width of the depletion region increase?
Awesome
Thank you a lot !!!!
But if the diffusion current is increasing, how is the depletion layer decreasing in size? Won't the rate of recombination increase with diffusion?
Your notes available? If available where to find them...reallly besttt teacher ever now a month left to my exams, no time to write lecutres as I've 3 days to prepare I wish O had find them before😢😢😢😢
Thank you sir
Electrostatics and circuits belong to one science not two. For a unified approach to learning Current and the process of conduction watch these two videos i. ua-cam.com/video/REsWdd76qxc/v-deo.html and
ii. ua-cam.com/video/8BQM_xw2Rfo/v-deo.html
Also, in the textbooks referred in the last frame of video i you will find descriptions of the operation of resistors, capacitors and inductors using this approach which makes it easier to understand.
There are also chapters in the textbook references which explain the operation of diodes and transistors using the unified approach and includes descriptions of forward and reverse biasing p-n junctions.
Q. True or False:
In a pn junction diod without any external potential source, the diffusion current and drift current are caused at the junction by-
1. Majority carriers for diffusion current
2. Minority carriers for drift current
3. No current at the junction
very nice and simple thank you
Please help me‼️‼️, how can holes travel to N region , they are just the vacant place where electrons lack right ???
Can you also please explain heterojunction energy band diagrams with the same simple explanations?
Is it conventional current?
Sir while Forward Biasing a PN Junction, there will be current flowing in both directions, right? Because both diffusion (major) and drift (minor) are happening. So there will be a tiny current flowing from N to P. So we can't use this Forward Biased PN Junction in daily life (as the main goal is to allow current to flow only in one direction)
In forward bias, the diffusion current is orders of magnitude larger than drift, so there is a high current from P to N.
In reverse bias, there is a very tiny drift current from N to P. In most applications this is negligible
Thus the diode acts as a one-way switch, conducts in the forward bias, but doesn't conduct (negligible conduction) in the reverse bias.
Hope this clarifies your doubt.
If the electrons are moving from battery to n region and filling the holes in p type region then why the flow of electrons/electricity is opposite in simulation?
Great video
what software are you using?
regardless of this awesome video ..
I AM SUPER CURIOIS TO KNOW, WHAT IS THE BRUSH TYPE AND SIZE THAT YOU USE IN SKETCHBOOK!! ..
please let me know
Shouldn't it be 1.1 eV for Silicon, and 0.7 eV for Germanium?
If diffusion increases won't all the holes and electrons recombine and get destroyed....then there will be no more particles to conduct.??
Good question. Let's think about electrons.
Towards N side terminals there are loads of free electrons (as most holes don't make it there). Think of this terminal as the source of electrons.
Now as these electrons diffuse into P side they keep recombining.
The lost electrons are replenished from that 'source'.
Okay so won't that 'source' eventually run out of electrons?
No. For every electron that moves out of it, it pulls an electron from the wire immediately next to it. That's how electrons move in the wire as well.
Let me know if this helps.
Oh......i get it now.....thanks a lot!!!
¡Thank you!
How does increase in diffusion current decrease the depletion layer? It doesn't make any sense coz diffusion caused depletion layer.. plz do reply this question..
The depletion layer decreases due to the external power voltage supplied.
This inturn increases diffusion because the depletion region was acting as a barrier for diffusion.
Khan Academy India - English Why is it not that the diffusion current increases and so the depletion layer again becomes wider due to it?
Hi! I just want to ask why the voltages in the neutral zones don't change when a forward bias is applied? Since we know that when voltage is applied to any component, there will be an electric field inside it which points from positive to negative, and since the diode originally has no electric field in its neutral zone to cancel it, shouldn't there be a voltage in the neutral zones? Is there some kind of mechanism that counteracts this?
That's a great question. We are doing a lot of assumptions here, and one of them is the negligible resistance in the neutral regions. This is similar to how we neglect the resistance in wires and assume no electric field there!
@@KhanAcademyIndiaEnglish Please help me‼️‼️‼️ please , how can holes travel to N region , they are just the vacant place where electrons lack right ???
@@proudnepali8388 Hole are the vacant space. Since the negative terminal of the battery is connected with n type semiconductor where electron are the majority charge carrier. And the positive terminal of the battery is connected with P type semiconductor where the hole are the majority charge carrier. Due to the repulsion between negative terminal of the battery and free electron as well as the repulsion between positive terminal of the battery and hole the depletion layer width decreases. So that the some energetic free electron migrates from n type semiconductor to P type semiconductor due to decrease in depletion layer(resistance decreases). Before migration in the n-type semiconductor there was neutral condition but after the Migration of some energetic electron there are generated some hole in the n type semiconducyor. So due to migration of free e there is some hole are generated. That we call migration of hole .
@@KhanAcademyIndiaEnglish Thanks for the response! I think that clears things up for me then
KINDLY MAKE THE MASTERS AND PHD LEVEL VIDEO
Thanks
Electron move from n type to p type for diffuse of their Barrier and back to the battery
Please help me, how can holes travel to N region , they are just the vacant place where electrons lack right ???
Hole probably doesn't travel to N region it's the other way the electrons from N region travels to the holes to fill them
@@soudipchanda2884 I had thought in same manner but I guess for simplified understanding the concept of diffusion is introduced here
If holes move towards electrons then why recombination not occurs??
I think recombination occurs ..
The current in diode back to battery
Why don’t the boron and phosphorus atoms just combine chemically and form boron phosphide instead of existing as separate layers just beside each other?? In an atom, the constant motion of electrons and the presence of neutrons altogether prevents the electrons from just collapsing into the positively charged nucleus, what stops boron and phosphorus from chemically combining here??
holes move?
Holes aren't any thing the are just the absence of elctrons
Am I seeing things or the arrow got brighter when increased voltage 😶
All the concepts you gave upto this point were great but this video has pretty low standard as far as concept is concerned... you should have talked about flow of electrons rather than saying holes are flowing and should have talked about conventional and electron current
There are two types of electrons. Free electrons that flow freely, and valence electrons (which are covalently bonded) which move from one 'hole' to another. These two motions are pretty independent of each other.
The free electrons literally move over some distance. But the valence electrons just jump to a neighbouring hole, virtually moving the hole in the opposite direction. Then the next neighbour will jump in and then the hole again moves (virtually). So you see these valence electrons are not really moving from one place to another (just jump to their neighbouring space and sit there). Hence it makes it both easier mathematically and intuitively to imagine that these 'holes' are moving. This is why we treat holes as a separate individual particle and consider it's motion in the valence energy region (just like how free electrons move in the conduction band region).
If you need more details on this, they are explained in previous videos, do check out the playlist. Hopefully, it would help.
Khan Academy India - English that’s an amazing explanation to distinguish between how we Conceptualise things for ease vs how it actually is. 👏👏👏
Your explanation is good but please stop with the fake accent sir. It's
seriously
irritating.
How on earth is that a fake accent?
You can _probably_ notice it if you watch other videos of the same lecturer
@@gold8780 yeah I have watched videos with the same lecturer. It's just an Indian accent, how is that fake?
@@gerrycalhoun9827 I guess it isn't an Indian accent that's why?
@@gold8780 The guy (Mahesh Shanoy) is an indian. From India. It's not fake accent, it's an indian accent. Because he's an indian, from India. Plus you're on a channel called Khan Academy India and you're complaining about an indian accent?
why does he use a fake accent
Well that is none of our business since we are here to learn and not to pass judgemental statements on his speech....
You wrongly thaught this theory
Please help me, how can holes travel to N region , they are just the vacant place where electrons lack right ???
The battery applies an electric field from positive to negative initially since diode is forward biased consider holes as +ve charge carriers for simplification