Semiconductors 

Semiconductors are unique materials that have neither the electrical conductivity of a conductor nor of an insulator. Semiconductors lie somewhere in between these two classes giving them a very useful property. Semiconductors are able to manipulate electric current. They are used to rectify, amplify, and switch electrical signals and are thus integral components of modern day electronics. 

Semiconductors can be made out of a variety of materials, but the majority of semiconductors are made out of silicon. But semiconductors are not made out of silicates, or silanes, or silicones, they are made out pure silicon, that is essentially pure silicon crystal.   Like carbon, silicon can make a diamond like crystal. This structure is called a silicon lattice. (see Figure 1) Silicon is perfect for making this lattice structure because its four valence electrons allow it too perfectly bond to four of its silicon neighbors. 

Figure 1: an example of a silicon lattice

However, this silicon lattice is essentially an insulator, as there are no free electrons for any charge movement, and is therefore not a semiconductor. This crystalline structure is turned into a semiconductor when it is doped. Doping refers to a process by which impurities are introduced into ultra pure silicon, thereby changing its electrical properties and turning it into a semiconductor. Doping turns pure silicon into a semiconductor by adding or removing a very very small amount of electrons, thereby making it neither an insulator nor a conductor, but a semiconductor with limited charge conduction. Subtle manipulation of pure silicon lattices via doping generates the wide variety of semiconductors that modern day electrical technology requires. 

Semiconductors are made out of silicon for two fundamental reasons. Silicon has the properties needed to make semiconductors, and silicon is the second most abundant element on earth.