Semiconductor devices are nothing but electronic components that exploit the electronic properties of semiconductor materials, like as silicon, germanium, and gallium arsenide, as well as organic semiconductors. Semiconductor devices have replaced vacuum tubes in many applications. They use electronic conduction in the solid state as opposed to the thermionic emission in a high vacuum. Semiconductor devices are manufactured for both discrete devices and integrated circuits, which consist of from a few to billions of devices manufactured and interconnected on a single semiconductor substrate or wafer.
Semiconductor materials are useful by their behavior which can be easily manipulated by the addition of impurities is known as doping. Semiconductor conductivity can be controlled by the electric or magnetic field, by exposure to light or heat, or by the mechanical deformation of a doped mono crystalline grid; thus, semiconductors can make excellent sensors. Current conduction in a semiconductor occurs free of electrons and holes, collectively known as charge carriers. Doping of silicon is done by adding a small amount of impurity atoms and also for phosphorus or boron, significantly increases the number of electrons or holes within the semiconductor.
When a doped semiconductor contains excess holes it is called “p-type”(positive for holes)semiconductor, and when it contains some excess of free electrons, it is known as “n-type”(negative for electrons) semiconductor, is the sign of charge of the majority mobile charge carriers. The junctions which formed where n-type and p-type semiconductors are joined together is called p–n junction.
A semiconductor diode is a device typically made up of a single p-n junction. The junction of a p-type and n-type semiconductor forms a depletion region where current conduction is reserved by the lack of mobile charge carriers. When the device is forward biased, this depletion region is reduced, allowing for significant conduction, when the diode is reverse biased, the only less current can be achieved and the depletion region can be extended. Exposing a semiconductor to light can produce electron hole pairs, which increases the number of free carriers and thereby the conductivity. Diodes optimized to take advantage of this phenomenon is known as photodiodes. Compound semiconductor diodes are also being used to generate light, light-emitting diodes and laser diodes.
Bipolar junction transistors are formed by two p-n junctions, in either p-n-p or n-p-n configuration. The middle or base, the region between the junctions is typically very narrow. The other regions, and their related terminals, are known as the emitter and collector. A small current injected through the junction between the base and emitter change the properties of the base collector junction so it can be conduct current even though it is reverse biased. This creates a larger current between the collector and emitter, and controlled by the base-emitter current.
The silicon (Si) is most widely used material in semiconductor devices. It’s having lower raw material cost and relatively simple process. Its useful temperature range makes it currently the best compromise among the various competing materials. Silicon used in semiconductor device manufacturing is presently fabricated into bowls that are large enough in diameter to allow the manufacture of 300 mm (12 in.) wafers.
Germanium (Ge) was a widely used in early semiconductor material, but its thermal sensitivity makes less useful than silicon. Nowadays, germanium is often alloyed with (Si) silicon for use in very-high-speed SiGe devices; IBM is a main producer of such devices.
Gallium arsenide (GaAs) is also widely used with high-speed devices, but so far, it has been difficult to form large-diameter bowls of this material, limiting the wafer diameter sizes significantly smaller than silicon wafers thus making mass production of Gallium arsenide (GaAs) devices significantly more expensive than silicon.