Current flow in semiconductors.

[kalee20]

Originally Posted by MajorWest

Do you think valves are actually better than semiconductors in terms of efficiency and given the fact current flows in a vacuum?

We all know that valves are far better than semiconductors here, don't we?

More seriously, devices using electrons in a vacuum have the potential to be better than solid-state devices in terms of electrical performance. The down side is that it's just not feasible to make them at the sub-micron dimensions of modern semiconductor foundries, so limiting factors such as transit times etc kick in rather earlier.

Originally Posted by MajorWest

Usually I start right at the beginning with the virtual cell. P material will automatically attract electrons from N material by virtue of the doped silicon.

It doesn't. P-type material (and N-type) don't have any net charge, so putting P-type in contact with N-type doesn't attract electrons. What happens is that, when in contact, electrons from the N-type just diffuse into the P-type (like putting a wet sponge in contact with a dry one). There's no pressure driving the flow. Then, as the electrons diffuse in, the N-type material is left with a slight shortage of electrons to balance the lattice charge, and the P-type with a surplus, and because unlike water electrons carry charge, there's an electric field set up which then opposes further diffusion and you get a depletion zone.

[Trish]

Originally Posted by kalee20

More seriously, devices using electrons in a vacuum have the potential to be better than solid-state devices in terms of electrical performance. The down side is that it's just not feasible to make them at the sub-micron dimensions of modern semiconductor foundries, so limiting factors such as transit times etc kick in rather earlier.

Your prayers just may have been answered with the arrival of nanoscale vacuum tubes.

----> http://www.newelectronics.co.uk/elec...noscale/45695/