What are semi-conductors and how do they work?
In: Engineering
You start with a material that on its own does not necessarily conduct electricity because the atoms are fairly “happy” with the amount of electrons they have, and aren’t very willing to accept electrons or pass them along to neighboring atoms. But then you add a small “contamination” of another material where the atoms have too many or too few electrons, and now this instability in the material helps encourage electricity to flow. Now the tricky part is when you put 2 areas next to each other where the contamination (doping) gives the material an excess vs. deficiency of electrons. Now these 2 materials prefer *different* conditions to best encourage the flow of electrons. As a result, electricity only flows in 1 direction across this gap, in the other direction, the conditions are backwards vs what those materials each need to conduct electricity. This is a diode, and already has some uses in electronics.
You can also add a thin layer in the middle with another junction, but this area isn’t filled with your “input” or “output” electricity, instead you apply a relatively small amount of power to it and you can therefore limit on increase the power through the whole device with a relatively small input signal. This makes a transistor, some variation on that idea is the basis of most newer electronics from radios to computers and electric car control circuits.
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