Semiconductors are essential components of electronic circuits and contain properties of both insulators, such as glass, and conductors, such as copper. Most semiconductors are crystals made of silicon or germanium. By introducing other elements in the crystal through doping, the crystals turn into semiconductors. Depending on the amount of electrons created by the doping process, the crystals turn into N-type semiconductors, or P-type semiconductors.
Data Source: Unified Global Standards (ISCED, ISCO, O*NET, ESCO)