Despite the fact that integrated circuits have largely replaced discrete electronic devices it is still important to know how the separate parts of those circuits work.
Conductivity of electricity take vital role when creating electric circuits. Sometimes electicity conductor is required, sometimes insulator. This is wear the so called semiconducting material comes in handy. Basically in normal room temperature semiconductors act like insulators, and when they are heated to a certain point they become conductors. Described differently when the temperature raises the covalent bonding in the semiconductor weakens and electricity starts flowing.