A semiconductor is a material with electrical conductivity between that of a conductor and an insulator, a crucial property that can be precisely modified. This modification is primarily achieved through doping, where minute amounts of impurities are added to create "n-type" (electron-rich) or "p-type" (electron-hole-rich) regions within the material. The interaction of charge carriers at p-n junctions, formed where these differently doped regions meet, is the fundamental principle behind most modern electronics, including diodes and transistors.

Silicon is the most critical semiconductor, with gallium arsenide being another significant material used in advanced applications like laser diodes and solar cells. These materials enable diverse properties such as variable resistance, sensitivity to light, and unidirectional current flow, essential for amplification, switching, and energy conversion. The journey of semiconductors began with the 1904 cat's-whisker detector, culminating in the transformative invention of the transistor in 1947 and the integrated circuit in 1958, which revolutionized the technological landscape.