Puolijohdekide

A puolijohdekide, or semiconductor crystal, is a crystalline solid material that possesses electrical conductivity between that of a conductor and an insulator. This intermediate conductivity is a key characteristic that makes these materials essential for modern electronics. The electrical properties of a puolijohdekide can be significantly altered by the presence of impurities, a process known as doping. Doping introduces either an excess of electrons (n-type semiconductor) or an excess of "holes," which are vacancies where electrons could be (p-type semiconductor).

The fundamental behavior of a puolijohdekide is governed by its electronic band structure. In the valence band, electrons are tightly bound to atoms. In the conduction band, electrons are free to move and conduct electricity. The energy gap between these two bands determines the material's semiconducting nature. If the energy gap is small enough, thermal energy or other forms of energy can excite electrons from the valence band to the conduction band, enabling conduction.

Common examples of puolijohdekiteet include silicon (Si) and germanium (Ge), which are elemental semiconductors. Compound semiconductors, such as gallium arsenide (GaAs) and indium phosphide (InP), are also widely used. These materials form the basis of nearly all semiconductor devices, including transistors, diodes, integrated circuits, and solar cells, playing a critical role in computing, telecommunications, and countless other technologies.