SEMICONDUCTORS

You might know by now that all kind of metals are conductors and they allow the electric current to flow.

The possibility for an electron to move through the conductor will be less then before if you heat the conductor up.

But not all the materials have got the same qualities :

There are some materials which behave like an insulator if the ambient temperature is at 25 °C. But if you heat them up then you will be able to use them as a normal conductor.

These metals which just conduct at certain conditions are called semiconductors.

But if we want to understand this phenomena then you will have to take a closer look at the structure of the material.

Let's take a look at a silicon atom : atom - go get a graphical browser

Every single proton has got four "neighbour electrons" ,that means that there are four electrons next to the center of the atom which cannot move away without external help. The electrons surrounds the core of the atom with a certain distance just like a sattelite the earth

But the single electrons are also used by the silicon atom next to it. That means that one electron surrounds two silicon atoms one by one.

So that is the reason why the construction of silicon is very strong and now you can also understand why this element is not able to conduct the electric current without external energy (for example heat).

So if you heat the material up, the electrons will start to move and if the energy is high enough the electrons will be able to move away from their fixed position. They are called free electrons.

electronic movement - interesting These free electrons will remain a hole when they leave their position. This hole was neutral and so it becomes positive, because the negative electron has left and this hole can be refilled by another free electron.

Now the electrons are able to move and if electrons move then we can call it an electric current.

So if you want to use the semiconductors at a normal ambient temperature you will have to increase the number of the free electrons or the number of the positive holes.

different atoms - important If you put some atoms into the silicon which have five electrons on its exterior track, you increase the number of the free electrons.

These materials are called n-material because they have got a negative charge.

Otherwise, if you put some atoms into the silicon which have just 3 electrons on its exterior track, you decrease the number of the electrons and increase the number of the positive holes.

These materials are called p-material, because they have got a positive charge.

This technology is used if you want to built diodes, which is the next topic of our small electronic course.

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