P-N JUNCTION BY Y.SANTOSHI (221710303065)

A p-n junction is a boundary or interface between two types of semiconductor material, p-type and n-type, inside a single crystal of semiconductor. The "p" side contains an excess of holes, while the "n" side contains an excess of electrons.

            
The invention of the p-n junction is usually attributed to American physicist Russell Ohl of Bell  Laboratories.However, Vadim Lashkaryov reported discovery of p-n junctions in copperoxide and silver sulphide photocells and selenium rectifiers  in 1941.

During the formation of a p-n junction , following two phenomenon take place:

• A thin depletion layer is set up on both sides of the junction and is so-called because it is depleted or devoid of free charge carriers.Its width is about 1 micrometer.
• A junction or barrier potential is developed across the junction whose value is about 0.3V for Ge and 0.7V for Si.

p-n junctions are elementary building blocks of most semiconductor electronic devices such as diodes, transistors,solar cells, LEDs etc.

 The  behaviour of the p-n junction with regards to the potential barrier's width produces an asymmetrical conducting two terminal device, better known as p-n junction diode.It is one of the simplest semiconductor devices around, and which has the characteristic of passing current in only one direction only.However, unlike a resistor,a diode does not behave linearly with respect to the applied voltage as the diode has an exponential current- voltage (I-V) relationship and therefore its operation cannot be described simply using an equation such as ohm's  law.