| Summary: | A semiconductor is a material with electrical conductivity due to the flow of electrons (as opposed to ionic conductivity) intermediate in magnitude between that of a conductor and an insulator. This means a conductivity roughly in the range of 10' to 10 siemens per centimeter. Semiconductor materials are the foundation of modern electronics, including radios, computers, telephones, and many other devices. Such devices include transistors, solar cells, many types of diodes, including the light-emitting diode, the silicon-controlled rectifier, and digital and analog integrated circuits. Similarly, semiconductor photovoltaic solar panels directly convert light energy into electrical energy. In a metallic conductor, the current is carried by the flow of electrons. In semiconductors, current is often schematized as being carried by the flow of electrons or by the flow of positively charged "holes" in the electronic structure of the material. In reality, however, only the movements of electrons are involved in both cases. Common semiconductor materials are crystalline solids, but amorphous and liquid semiconductors are known. These include hydrogenated amorphous silicon and mixtures of arsenic, selenium, and tellurium in a variety of ratios. These compounds share with most well-known semiconductors an intermediate conductivity and a rapid variation in conductivity with temperature, as well as an occasional negative resistance. Such disordered materials lack the rigid crystal structure of conventional semiconductors such as silicon and are generally used in thin-film structures, which are less demanding on the electronic quality of the material and thus relatively insensitive to impurities. and radiation damage. Organic semiconductors, ie organic materials with properties resembling conventional semiconductors, are also known. Silicon is used to commercially create most semiconductors. Dozens of other materials are used, including germanium, gallium arsenide, and silicon carbide. A pure semiconductor is often called an "intrinsic" semiconductor. The electronic properties and conductivity of a semiconductor can be changed in a controlled manner by adding very small amounts of other elements, called "dopants", to the intrinsic material. In crystalline silicon, this is typically achieved by the addition of boron or phosphorous "doping" impurities. to the melt and then allow the melt to solidify into the glass.
|
|---|