Semiconductors and semiconductor materials are used to fabricate microelectronic devices and optoelectronic devices such as transistors, photodetectors and solar cells. Semiconductors and semiconductor materials are useful because their electrical conductivity can be altered with dopants, an applied electric field, or electromagnetic radiation. Silicon (Si) is the most commonly used semiconductor material today; however, other semiconductor material types are also available.
The number of valence shell electrons in a semiconductor material places this category of material between insulators (poor electrical conductors) and metals (good semiconductors). Insulators have a filled valence shell (eight electrons) and a large band gap, which results in poor electrical conductivity. Metals have a partially-filled valence shell and overlapping band gap, which results in free-traveling electrons and high electrical conductivity.
The first semiconductors and semiconductor materials produced electrical conduction through contact with a metal wire. Subsequent technologies used semiconductor crystals and semiconductor diodes. A semiconductor diode allows current to flow in one direction only.
There are many applications for semiconductors and semiconductor materials in materials engineering, such as the fabrication of transistors, photodetectors and solar cells.
In semiconductor manufacturing, transistors are placed together to create a silicon chip. The semiconductor manufacturer than creates a microprocessor from the silicon chip.
There are two basic categories of semiconductors and semiconductor materials: electrical semiconductors and compound semiconductors. Silicon (Si) and germanium (Ge), the most common electrical semiconductors, are used in many semiconductor components. Gallium arsenide (GaAs) and indium phosphide (InP) are examples of composite semiconductors that contain added materials or dopants. Semiconductor doping, the addition of a very small amount of a foreign substance to a pure semiconductor crystal, provides a semiconductor with an excess of conducting electrons or an excess of conducting holes.
ASTM F42 - These test methods cover the determination of the conductivity type of extrinsic semiconductors. While explicit details are given for germanium and silicon, inclusion of other extrinsic materials such as gallium arsenide and indium anti-monide should be feasible.
ISO 22197-1 - This part of ISO 22197 specifies a test method for the determination of the air-purification performance of materials that contain a photocatalyst or have photocatalytic films on the surface, usually made from semiconducting metal oxides
ISO 27447 - This International Standard is intended for use with different kinds of semiconducting photocatalytic materials used in construction materials, in flat sheet, board, plate shape or textiles that are the basic forms of materials for various applications.