n-channel enhanecement MOSFET - working: why is it an n-type inversion layer?

In this MOSFET, when we apply a +ve voltage to the Gate, we repel holes as the majority charge carrier in the p-type substrate downwards, thus uncovering fixed acceptor ions/atoms which are now negativly charged (electrons in the substrate are drawn to this region under the Gate).

We thus create a layer of fixed negative ions (a acceptor atom with a electron) and Sedra calls this newly formed structure a n-type inversion layer.

But in n-type materials we normally have fixed donor atoms that have donated an electron and are now +ve ions.

So.. n-type == '+ve dopant ion, plenty of e' inversion == '-ve dopant ion'

What am I interpreting incorrectly?

Reply to
Veek M
Loading thread data ...

If you haven't crossposted this to sci.e;ectronics.design you probably shou ld. this is definitely not a basic question. It has to do with basic semico ndutors but alot of people, most engineers don't have to know too much abou t that kind of stuff. Give them the spec sheets and they design stuff.

Some of them come here, but some of them stay over in design because of stu pid questions. Yours is not a stupid question by any means. I just go by th e spec sheet so I am useless for a question like this. It is like another b ranch of the science.

I assume you've aready wikied it and their content was not adequate.

Reply to
jurb6006

thanks for the heads up.

it's in Sedra which is pretty basic.. you should see: Sze - Physics of Semi, that's really hairy :)

thanks.

didn't check on the wiki till after you suggested it, but yeah, pretty much doesn't explain the reason for why it's called: n-type inversion.

Reply to
Veek M

The 'inversion layer' is still p-type material (as a material property, in equilibrium, it has free holes and not free electrons). But, once the gate repels the holes, n-type carriers from the end regions (the drain and source) can freely travel in that region, and conduction occurs due to those minority carriers, in that channel.

So, the conduction is n-type (electron) conduction, though the material is p-doped. If there weren't any gate voltage, the electrons couldn't travel through, because they'd react (recombine) with the free-traveling holes.

Reply to
whit3rd

I found this link super helpful in clarifying things:

formatting link
you guys can check it out.

The key is the n+ doping which creates a asymmetric junction that allows tunelling from S->G thus introducing charge carriers.

Reply to
Veek M

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.