semiconductor diode

In electronics, a two-terminal semiconductor device that allows electric current to flow in only one direction, the forward-bias direction. A very high resistance prevents current flow in the opposite, or reverse-bias, direction. It is used as a rectifier, converting alternating current (AC) to direct current (DC).

The diode is cut from a single crystal of a semiconductor (such as silicon) to which special impurities have been added during manufacture so that the crystal is now composed of two distinct regions. One region contains semiconductor material of the p-type, which contains more positive charge carriers than negative; the other contains material of the n-type, which has more negative charge carriers than positive. The region of contact between the two types is called the p–n junction, and it is this that acts as the barrier preventing current from flowing, in conventional current terms, from the n-type to the p-type (in the reverse-bias direction).