I have had a request to present a burst on semi conductors. I hope its easy to understand, haven't done this for years.
The basic building blocks for semi conductors start with quad valency elements (meaning 4 electrons in the outer orbit) such as silicon and germanium. Now by themselves these elements are insulators.
The next building blocks are tri valency elements with 3 electrons in the outer orbit (from memory there are 3 and I have forgotten them, but I recall arsenic, antimony as likely suspects, correct me if im wrong please)
Then the penta valency elements with 5 electrons in the outer orbit.
OK, our major element in all of this is silicon (4 electrons), an insulator called the substrate. IF we chemically add a tri valency element we create a "space" or "hole" for where an electron can sit due to co valent bonding. This is called P type material.
Now lets add penta valency material in co valent bonds to silicon. Due to the bonding we have an electron outside the bond. This is called N type material and is free to move about the material (free electron = conductor)
When we join these together as a PN junction a lot of great stuff takes place. Just like building a girls school on the back wall of a boys school there will be a migration of negative electrons from the N type material across the join (or barrier) to take their place in the spaces in the P type material. This migration doesn't wait till the lights are out, it happens the instant these materials are joined together.
OK now for the electronic magic, as these electrons pass over the junction or barrier of these materials they leave behind a fully bonded combination that is an insulator, likewise when the electron from the N side meet the P material the bonding is completed and it becomes an insulator as well. Therefore in its no external voltage state the device is a high value resistor.
Next post will be what happens when a voltage is applied to this beast. BTW its called a PN junction at this stage.
Cheers
PS. here is an interesting video on what I have been talking about:
www.youtube.com/watch?v=5ZNeDxfgYAE
the dialogue is a bit deep but makes some good points.
-- Edited by Crockie on Friday 26th of December 2014 05:55:52 PM
Good work, can't wait till the next installment, though i'd forgotten a lot of this stuff, but like riding a bike, you never forget, just takes a little longer to a recall. Must be a old age thing.
Good work, can't wait till the next installment, though i'd forgotten a lot of this stuff, but like riding a bike, you never forget, just takes a little longer to a recall. Must be a old age thing.
Keep it coming !!!!
Cheers mate, its fun writing this stuff, keeps the grey cells active and hopefully doing people some good. Im not too sure how I can make AC theory simple....
It's good reading this post and remembering what I was taught back in the 60's,I just hope I don't need to use the theory again,not that I used it much after graduation in 1973. As for the A.C. theory Phil, it's easy....DON'T DO IT......cheers Peter. That will bring back some memories,it was confusing then and even more confusing now..grey matter problems as valiant 81 said.......Must be an old age thing...Keep it up Phil,it's good reading . cheers Peter.
-- Edited by 2foot6 on Friday 26th of December 2014 09:17:14 PM
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Some political leaders and babies nappies should be changed often for obvious reasons.
It's good reading this post and remembering what I was taught back in the 60's,I just hope I don't need to use the theory again,not that I used it much after graduation in 1973. As for the A.C. theory Phil, it's easy....DON'T DO IT......cheers Peter. That will bring back some memories,it was confusing then and even more confusing now..grey matter problems as valiant 81.......Must be an old age thing...Keep it up Phil,it's good reading . cheers Peter.
Welcome aboard Peter, yes AC theory will be a challenge but I think the readers will be up to it. Im working on tomorrows episode ACDC..
The first lesson I had to present trade apprentices was semiconductors (which I love) but the deeper theory was a bit tough, didnt have youtube in those days.
and I thought a geranium was a flower - no - don't beat me up - just kidding, and realize its spelt differently.
I was never a techo and too old now to try to understand it - I just stick to looking a pretty ladies when we're out shopping and the wife is asking me (but wont take on my opinion) to get a 300 or 325gm of whatever
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Cheers Bruce
The amazing things you see when nomading Australia
the bonding is completed and it becomes an insulator as well. Therefore in its no external voltage state the device is a high value resistor.
