Semiconductor Devices and Applications

Semiconductor devices are electronic components that exploit the electronic properties of semiconductor material principally silicon germanium and gallium arsenide as well as organic semiconductors. Semiconductor devices have replaced thermionic devices (vacuum tubes) in most applications. They use electronic conduction in the solid state as opposed to the gaseous state or thermionic emission in a high vacuum. Semiconductor devices are manufactured both as single discrete devices and as integrated circuits (ICs) which consist of a number – from a few (as low as two) to billions – of devices manufactured and interconnected on a single semiconductor substrate or wafer. Semiconductor materials are useful because their behaviour can be easily manipulated by the addition of impurities known as doping. Semiconductor conductivity can be controlled by the introduction of an electric or magnetic field by exposure to light or heat or by the mechanical deformation of a doped monocrystalline grid; thus semiconductors can make excellent sensors. Current conduction in a semiconductor occurs via mobile or free electrons and holes collectively known as charge carriers.