The PN junction diode is made up of semiconductor material. It is always conducted in one direction and hence used for rectification. The PN junction diode has two terminals namely anode and cathode. The current flows from anode to cathode.
The PN junction diode conducts only when it is connected in forward biased. The symbolic representation of PN junction diode is shown in the figure above. The arrow head represents the positive potential, and the bar shows the negative potential of the diode.
The PN junction diode has a P-type and N-type semiconductor material which is joined by the process of alloying. Thus, both the ends of the diode has different properties. The electrons are the majority charge carrier of the N-type material, and the holes are the majority charge carrier of the p-type semiconductor material. The region in which both the p-type and n-type material meets is known as the depletion region. This region does not have any free electrons because electrons and holes combine with each other in this region.
The depletion region is very thin, and it does not allow the current to flow through it. The PN junction starts conducting when the forward bias is applied across the junction. The forward bias means the P-type material is connected to the positive terminal of the battery and the N-type material is connected to the negative supply.
The forward biased creates the electric field which reduces the depletion region of the PN-junction diode. When the potential barrier is completely reduced, it creates the conducting path for the flow of current. Thus, large current starts flowing, and this current is called the forward current.
