What are the Semiconductor Devices?

A semiconductor is a material whose conductivity is much less than a conductor (such as copper), but greater than that of an insulator (such as glass). Selected impurities can be added to a semiconductor to give it certain desired characteristics. One part per million of arsenic might be added to germanium to provide free or loosely held electrons. This substance is called “donor” or N-type material. If gallium is used as the impurity, the crystal has a lack of electrons or “holes” in its structure. This substance is called “acceptor “ or P-type material. (In both N-type and P-type crystals, the crystal as a whole is electrically neutral.) .

When a P-type crystal is grown next to an N-type crystal, a P-N junction is formed. Electrons can flow easily only in one direction. This is one type of diode that can be used to change alternating current (AC) to direct current (DC) by blocking any negative current: another term for this process is rectifying.

A transistor has two junctions. There are P-N-P transistors and N-P-N transistors. Many diodes and transistors can be grown on a very small piece of silicon or germanium in useful combinations called integrated circuits. A transistor can primarily be used to amplify a signal. The transistor uses energy from an external source, a battery or power line, to create an output signal that is a reproduction of the input signal but with much greater amplitude. Many diodes and transistors work together to make your computer function.