Nowadays you will be able to find semiconductors around every corner in your phone laptop and even on your UCL ID card. So, it is important to understand how they work and what exactly they are used for.

The semiconductor is a substance that has its conductivity being bigger than insulators but smaller than most metals. There are many semiconductor elements and compounds but I will use silicon as it is one of the more common elements in the universe and when it is pure it forms a nice tetrahedral structure. 

As it has no free electrons they only conduct current when outer electrons have enough energy to escape from the bond and travel through the structure. The electrons from surrounding bonds fill in the positive holes created by the previous electrons. You can increase the chance of that happening if you add more energy to the electrons by heating. Let’s say they will leave the bonds more readily, therefore, conduct or current.

Semiconductor properties can be altered by using doping. This is when you purposefully add impurities to achieve desired electrical behaviour.

There is N-type and P-type doping. In P-type an atom with only three electrons in its outer shell in this case boron is placed in the structure, therefore, forming a positive hole that can move around, therefore, transmitting current.

In N-type an atom with five outer electrons is placed into the structure in this case, phosphorus, therefore, giving a free electron that can easily move around and transmit current.

These doped semiconductors can be used to create PN and NPN junctions more commonly known as diodes and transistors which have shaped our current world today.