DIODE

A diode is a two-layer (PN-junction) device which facilitates conduction in one direction and stops conduction in the other direction.

It has a wide range of applications like rectification (converting ac to dc), voltage regulation, protection against high voltage and wave shaping.

Furthermore, there are special purpose diodes, e.g. Zener diode, light-emitting diode and several others.

PN-JUNCTION DIODE

the junction is formed when thin layers of P- and N-type semiconductors are joined together that results in following phenomenon immediately.

• The majority holes from P-side diffuse into N-side and vice versa.

• This is the depletion region where no free electrons and holes are present.

• The electric fi eld set up by the positive and negative ions prevents further flow of electrons and holes.

• The electric fi eld causes the movement of minority carriers in opposite direction thatprovides a minority carrier drift current.

• In steady-state, there is no net current flow across the junction.


Working of PN Junction diode:

Some of the holes from P region move to N region and some of the electrons from N region is move to P region. Ions are formed by losing or gaining electrons from the other atoms.
 
So negative ions are formed in the P type region near the junction and positive ions are formed in the N type region near the junction. Negative ions have more number of electrons than protons and hence it is negatively charged. 

Positive ions have more number of protons than electrons and hence positively charged. These charges formed in the junction are immobile. This forms like the barrier at the junction and does not allow free electrons or holes from moving to the other side.