At the potential barrier, all that atoms are "satisfied"; they each have the appropriate number of electrons in their valence shell since the free electrons on the n-type side fill the holes on the p-type side. According the videos I have watched, when the gate is on, the electrons in the junction flow up into the gate to produce the emitter current. But these electrons are "satisfied" so why does this happen? Is it because the gate potential difference is high enough? or something else?

  • $\begingroup$ Lets say you have n-type source and drain, and p-type under the gate. You can't get electrons to go n->p->n. But, if you apply positive charge on the gate electrode, you pull electrons up next to the gate dielectric (think of the gate as a capacitor). If you can pull enough electrons, you can invert the material under the gate so it is now (essentially) n-type, so electrons from the source will happily flow over to the drain. $\endgroup$ – Jon Custer Apr 17 at 20:20

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