What Is a Semiconductor?

Semiconductors, most commonly silicon, form the backbone of modern electronics. Pure silicon is a poor conductor, but by adding tiny amounts of other elements (doping) — phosphorus for extra electrons (n-type) or boron for electron "holes" (p-type) — its conductivity can be precisely tuned. Joining n-type and p-type regions creates a p-n junction, the basis of diodes and transistors. Modern microprocessors contain billions of transistors etched onto silicon chips, each acting as a tiny switch. Semiconductors also power LEDs, solar cells, and laser diodes.