Equilibrium carrier concentration

[@udaytewary3809]

Really thankyou for this lecture sir❤️❤️❤️❤️❤️ and due to you only today I got to know the clear visualisation of doping and some idea about current and once again really thankyou sir ❤️❤️

[@kaushikdey9171]

This is a very very nice 👍👍👍👍 and rich of concepts.........i really fall in love with this lecture.

[@arup812]

28:00 we increase dopping from left to right so electrons are too much in right side.. if diffusion happens electron will go from right to left that means electric field will work from left to right ... ain't I right ?

[@amitkumar-sh2lk]

this doubt i also have , but direction of field we find by slope . if balls rolls down slope that means electrons flow in down slope direction means electric field will be opposite to electron flow . so here electric field will be from right to left . field are of two types drift elctric field and diffusion electric field . drift field is from right to left because its direction is opposite to flow of electon . whereas diffusion electric field is from left to right because due to diffusion electron flow from right to left . diffusion is due to concentration gradiant , whereas drift is due to electric field we apply .

[@imrphysicist6265]

correct

[@ramtripathi1621]

Yep I also think the same

[@Neeraj-is1jt]

​​@@amitkumar-sh2lk but here we didn't apply any electric field it's just the concentration gradient Can u please tell how me the gradient electric field arises i.e. it's origin? Sir explains slope in electric field due to difference in concentration at end points,did he attached any external source ? Plz let me know

[@amitkumar-sh2lk]

@@Neeraj-is1jt bro since concentration gradient is present here. more electrons are on right and less electrons are on left. so diffusion of electron happens from right to left. so obviously if diffusion happens then current will flow, but currents cant flow without battery and as here also no battery is connected so no current can flow, but due to diffusion current as electrons are moving from right to left then current must flow, so to counter or to stop current flowing equal amount of electric field created internally in this doped semiconductor to counter the flow of electron. so electric field direction is from right to left which create drift to electrons.

[@louerleseigneur4532]

Awesome Thank you very much sir

[@arup812]

can anyone explain in 25:44 ,, we doped the semiconductor gradually that means we increase number of electron in conduction band (which doesn't reduce band gap) which will increase farmi level gradually . that means the slop should happen in fermi level .... then why sir draw it in conduction band ?

[@amitkumar-sh2lk]

slope in fermi level come only when current is flowing , here since we have not connected any battery so current cant flow . so fermi level slope must be zero . less doping means Ec-Ef is more , high doping means Ec-Ef is less . so obviously in left side Ec-Ef should be more and in right side Ec-Ef is should be less , and since Ef has zero slope so obviously Ec and Ev will till and get slope .

[@ravishankarmishra2903]

I'm impressed 😶

[@ayushpatil7150]

very nice

[@nitishgupta169]

14:27 ,, sir n = total no of electrons.( Doped + intrinsic) U taken only doped electrons ??? Why

[@AtulKumar-ke8gq]

Because no. Of electron without doping is much much smaller than doped electron...........as sir also told earlier without doping electron concentration will be 10^10....and no.of doped electron is 10^17.....so 10^10 + 10^ 17 = 10^17 ( nearly) ... Thank you

[@nitishgupta169]

@@AtulKumar-ke8gq thank u bro👍👍. Happy Republic day 😊

[@ravikumarsharma3483]

Sir, intrinsic semiconductors are those materials where no doping is done, but here you are using the expression of n and p simplified based on moderate doping (From the last lecture). Please let me know how and why are you using this equation in intrinsic semiconductor concentration calculation?

[@imrphysicist6265]

same doubt

[@ramtripathi1621]

The formula stays the same for moderately doped semiconductor as well as for the intrinsic semiconductor as per maxwell approximation.

[@vishalsathiaseelan679]

Thank you so much sir🙏🏼🙏🏼

[@Rittiuu]

Wow ❤

[@Likhitha0912]

why is fermi level is still straight 28:05

[@dhirendratiwari9956]

Very good lec

[@aishwaryasingh5144]

Can any1 explain the concept of EF in the example tought, as Due to concentration gradient (diffusion) we have electrons moving higher conc. To lower conc. (opposite of slope) And in case of drift electron travel in the direction of slope.... So what is the overall direction of field

[@RahulKumar-rf7yc]

The direction of the net electric field will be from highly doped n-type side to lightly doped side when the sample is under equilibrium. One can also confirm that by the fact that at equilibrium there is no current, as the direction in which electron diffuse is opposite to the direction in which the electron experiences force due to field, thus zero current.

[@nitishgupta169]

@@RahulKumar-rf7yc Yes , moreover I think sir told concept of electrons rolling down the wedge just for understanding the direction of field only . In actual it does not happen

[@santhoshkumar-pn8gk]

Donor and acceptor Ionization energy levels of n-type and p-type respectively exist in the forbidden energy gap. But according to the definition of forbidden energy gap, there shouldn't be any charge carriers within that gap. Could anyone please explain me this one.

[@OverloadedSense]

Donor and acceptor ions are not charge carriers. They are immobile. Electrons and holes are the charge carriers which do not reside in the forbidden gap unless there is some trapping mechanism involved.

[@Neeraj-is1jt]

​@@OverloadedSense In previous lecture teacher clearly said that electron jump from donor energy level to conduction band you can see it's at 19:30 of previous lecture

[@manikantasingha6795]

Hello Sir, how does ELectric Field oppose to flow of electrons? It should rather enhance the flow of electrons. Please provide me an explanation Sir.

[@Neeraj-is1jt]

It didn't oppose the motion it's only in direction opposite to electron motion

[@thoughtcloud8869]

Glad if someone clear this doubt.. In this lecture, in a problem solved, the number of holes came out to be in power of 3. Where as in intrinsic Si, it is in the power of 10. How does there occur a tremendous decrease in holes?

[@akshat1601]

The example is not for intrinsic SC, it is of N-type SC. As donor dopant is added it will decrease the no. Of holes.

[@nitishgupta169]

As electron are in great number ,so some of them just recombine with the holes , hence quantity of holes decreases.

[@amitkumar-sh2lk]

@@nitishgupta169 thanks bro . this is correct explaination.

[@nitishgupta169]

@@amitkumar-sh2lk 😊😊 welcome 👍👍

[@sanjusingha1714]

Note 15:26

[@saikrishnagarlapati3937]

if E is the potential energy of the electron and how is it infinite at infinity ?Where is the reference point ?Similarly where us the reference point for the potential energy of holes?Please explain how and why those limits of integration while calculating the carrier concentration.

[@amitkumar-sh2lk]

bhai for electrons carrier concentation always start from Ec to infinete and for holes it is -infinte to Ev

[@Neeraj-is1jt]

I have a Doubt 1. here we didn't apply any electric field it's just the concentration gradient Can u please tell how me the gradient electric field arises i.e. it's origin? Sir explains slope in electric field due to difference in concentration at end points,did he attached any external source ? Plz let me know

[@MMTRINATHSOLASA]

THNQ sir

[@lakshitjain6852]

Aur Sodani, kesa he?

[@rahulyadav-ls9dh]

badiya bhai

[@agentwalker7045]

Everything is perfect . But the only thing is the course is not that much structured . For every topic the topic name should be mentioned , and when it's over it should also be mentioned . It is just feels like its just going and going and going .....

[@gugulothganesh_rguktb1478]

KT=0.026ev?

[@HustlerMohit]

Multiply boltzman constant to room temperature.