Pooljuht

Pooljuht, the Estonian term for semiconductor, refers to a solid material whose electrical conductivity lies between that of a metal and an insulator and can be controlled by external factors such as temperature, light, electric field, or by impurity doping. In intrinsic semiconductors, charge carriers (electrons and holes) are few, but their numbers can be increased dramatically with energy input or doping, enabling precise control of current flow. Doping introduces donors or acceptors to create n-type or p-type material, which forms junctions essential to device operation.

The most widely used pooljuht is silicon (Si), chosen for its abundance, thermal stability, and the native oxide that facilitates manufacturing. Other important materials include germanium (Ge) and compound semiconductors such as gallium arsenide (GaAs), gallium nitride (GaN), and indium phosphide (InP). The properties of these materials—band gap, carrier mobility, and breakdown voltage—determine their suitability for different applications, from high-speed electronics to optoelectronic devices.

Key devices based on pooljuht principles include diodes, which conduct current predominantly in one direction via a p–n junction, and transistors, which can amplify or switch signals. Transistors come in various forms, including bipolar junction transistors (BJTs) and metal-oxide-semiconductor field-effect transistors (MOSFETs). Modern electronics rely on integrated circuits that combine millions or billions of semiconductor devices on a single wafer.

Manufacturing involves growing a crystalline wafer (often via the Czochralski or float-zone method), doping selective regions, and patterning using lithography, deposition, and etching. Pooljuht technology underpins computing, communications, solar energy, and countless consumer electronics, and continues to evolve with new materials and device architectures.