Geek help: Gate Electrode?

[danaeris]

I'm trying to understand resonant tunneling transistors so I can make a question about them.

They apparently use a circuit element called a "gate electrode." The description talks about a voltage applied to this thing, and it has a + sign in the diagram. Is the voltage being applied ACROSS the electrode? The picture doesn't indicate two parts to the gate electrode, so I'm confused about this voltage which is supposedly across it.

Anyone able to enlighten me on this?

Comments

[bk2w.livejournal.com]

Not familiar with resonant tunneling transistors, but what I can find online suggests they have similar structures to field-effect transistors.

For FETs, the gate doesn't actually connect to anything else, nor does it conduct any electricty. Electrically, it cats like a captirPutting a high voltage on the gate creates an electrical field that attracts electrons in the transistor channel to the gate. This allows more and more electrons to flow through the channel from the emitter to the collector.

The "across" you're looking for is the voltage difference between the gate electrode and the channel/substrate immediately below in the transistor structure.

[danaeris.livejournal.com]

OK, I know you may be really busy and not have time to explain this one to me, but I have to ask because this explanation did not really clarify much for me, sadly.

You wrote:
Electrically, it cats like a captirPutting a high voltage on the gate creates an electrical field that attracts electrons in the transistor channel to the gate.

It looks like that sentence got cut off. Even if I try to fill in the blanks as "acts like a capacitor" I'm still mystified as to what the gate electrode does.

A resonance tunneling device simply conducts current when a voltage is applied across it, but not otherwise. The voltage increases the energy in the quantum dot in the center so that its energy levels line up with those outside of it, and the electrons are able to tunnel (quantum tunneling) due to the resonance (aka, the energy levels lining up). If the electrons can tunnel through, they can basically just travel through the entire device without any difficulty, so its sort of like a voltage activated switch.

A resonance tunneling transistor is supposed to be a resonance tunneling device with a gate electrode added in on top of the quantum dot, and that addition changes its function to that of amplifying the varying voltage applied to the gate electrode. So supposedly, you put a voltage across the gate electrode in addition to a small voltage across the entire thing, and combined these cause the energy levels to line up, resonance occurs, and the device conducts again all the way across.

OK, so I think I now understand what the gate electrode does... all it is is a method for applying a voltage JUST across the quantum dot, as opposed to the entire device. What I don't understand is why this amplifies anything. With the device, you put a potential difference across the whole thing and if it is one of the right amounts (ie. causes one of the quantom dots' energy levels to line up), it conducts. With the transistor, you've got a small voltage that isn't the right voltage applied across the whole device, and another voltage applied just to the gate/quantum dot, and they line up and the thing conducts. How is the end result different, and where does the amplification occur?

Hmm, I think I'll repost most of this as another entry. Thanks for the response. Even though it wasn't helpful, thinking about your answer clearly got me somewhere useful that I wasn't before.

[bk2w.livejournal.com]

Wow, yeah that comment got messed up somehow. Very odd.

[danaeris.livejournal.com]

Actually, I explain it all better in the new post, so you might do better to read that. It's very similar to what I wrote here but some things are more clear because I proofread and edited it. :) So if you should choose to try to figure this out, feel free to check that out.

Thanks either way!

[auros]

It seems to me there's a different term for the thing I'm thinking of, so I wouldn't take it particularly seriously... but I know that there's a variety of electronic component which only allows electrons to flow in one direction. That is, applying a voltage one way causes electrons to flow, but if you swap the terminals that are the source of the voltage, the electrons won't flow back the other way. (Is that a diode? Guh. I can't remember my EM or Circuits stuff at all. *sigh*)