Because khan academy from the very beginning wants to focus on India to spread free quality education (you can see several interview with indian medias out there) to the masses. And sal also has an indian root so that might played some sort of role.
This channel is just awesome. It deserves the best. Really, the teachers here at KHAN ACADEMY are super cool and make our concepts crystal clear and much easy. Not like that at my school. Really hat's off. Salute from me.
Sir In Previous Video You Said That When An Electron Jump From Valance Band To Conduction Band It Leaves A Vacant Space Which We Call Hole. By Same Logic In Doner Level Also When Electron Will Jump From Doner Level To Conduction Band Then It Should Also Leave A Hole In Doner Level. In That Case In Extrinsic Conductor Also The Number Of Holes And Electron Should Be Equal. But You Are Saying That In Extrinsic Semiconductor The Number Of Electrons In Conduction Band Is Greater Then Number Of Holes.....How Please Explain.??
Great question! Holes are left behind when an electron jumps from covalent bonds (in the Valence band) to the conduction band. The donated electrons were NOT covalently bonded! So, they don't leave behind a hole (in the donor level).
wont the group 15 and group 13 elements that are used to dope the semiconductor have there own conduction bands separate form the si / gr atom's conduction bands?
Excellent question. Since the doping level is extremely low. We can assume the doped atoms are isolated. And isolated atoms would just have discrete energy levels & not bands.
Thank you soo much I 've always had a doubt abt this N type and P type being neutral but it never occured to me that the atom we add becomes an ion!🥴 Thank you soo much again for teaching the whole thing🤩
In case of semiconductor the absence of electron at particular place in an atom is called hole . But y can't we say the same concept in case of a conductor because here also electrons move from valence shell
@@p.harika If i explain you this quantum mechanically to conduct electricity an electron needs to be in superposition of two different energies so in valence band when a hole is created an nearby electron in valence band could be excited by thermal agitation and it could be in superposition of two energy states at the same time. It is like the same thing that electron can have probability of being found at two different places at the same time.
I don't know, but I think they only can't have the same energy level when their atoms are "connected". All those electrons would be from separated phosphorus atoms which are far from each other, each having its own *exclusive* energy level at that height.
Sir, please clarify my doubt. Firstly, thankyou so much for the amazing best video. My doubt is that...here, in ntype semiconductor, no of electrons are greater than no. Of. Holes. ACCORDING to, recombination, the electrons should fall into holes. Because, there are so many electrons. Then finally, there should be no holes in the ntype semiconductor. Please kindly clarify my doubt sir, please
Yes it does happen and along with that the generation process also keeps happening since it is a spontaneous process and moreover the rate of recombination is same as the rate of generation so always the no of electrons is higher than the number of holes
Since silicon has its own conduction band phosphorus should also has it own conduction band it's should move there after excitation . Please explain it will be obliged Regards
A conduction band is more like a shared band, a band that belongs to all the atoms, that's why the electrons there conduct. So, even if valance bands are different for Si and P, the conduction bands are one single overlapped band. One can imagine the valance band as due to an inner orbital that doesn't touch with an inner orbital of the other atoms, while a conduction band corresponds to the outer orbital that touches and overlaps with the outer orbitals of other atoms, therefore becoming more like one large orbital spanning the whole crystal.
when we have only silicon atom at room temperature no. of electron is equal to no. of holes. as generation process still recombination happens the ne=nh right. after doping, if phosphorous donate one free electron also we get one hole so how this N-type get holes minority and electrons majority, pls explain.
Great question. For doping to make sense the energy level of the extra electron (for pentavalent) / the vacancy (for trivalent) need to be close to the conduction band (so electrons can easily jump) / valence band (so the electrons from valence band can jump creating holes). This will only be true for group 15 & 13. Keep asking these great questions :)
Naresh Yadav no, because the electrons are so tightly bound to nucleus ( remember c is small in size, in the first period ) if you add that as dopant, you’d require a lot of energy to excite those electrons , which is ultimately not beneficial
It looks to me like the reason the positive phosphorus ions don't behave like holes is because the free electrons don't fall into them. They move into the conduction band and stay there with what little heat it takes to get them there. With intrinsic Si, the current movement occurs by electrons falling into Si holes and being pulled out. (I may be wrong.)
after losing 1st electron phosphorus becomes +vely charged. So its effective nuclear charge (Zeff) increases. So it is not easily possible for phosphorus to give 2nd electron. Hope it helps :)
