A PN-junction is formed when an N-type material is fused together with a P-type material creating a semiconductor diode. In the previous tutorial we saw how to. This article discusses about P-N junction diode, diode theory of zero bias, forward bias, reverse bias with V-I characteristics and its applications. PN Junction Diode. If a suitable positive voltage (forward bias) is applied between the two ends of the PN junction, it can supply free electrons and holes with the extra energy they require to cross the junction as the width of the depletion layer around the PN junction is decreased.


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In other words, cathode terminal is the source of holes, the holes begins their journey at positive or cathode terminal and occupies the electrons position in the n-type semiconductor.


The free electrons in the n-type semiconductor gets attracted towards the positive terminal. The holes from the positive terminal cannot move towards the negative terminal because the wide depletion region at the p-n junction opposes the flow of holes.

The P-N Junction

Silicon and germanium semiconductor diodes For designing the diodes, silicon is more preferred over germanium. The p-n junction diodes made from silicon semiconductors works at high temperature than the germanium semiconductor diodes.

Forward bias voltage for silicon semiconductor diode is approximately 0. Silicon semiconductor diodes do not allow the electric current flow, if the voltage applied on the silicon diode p n junction diode less than 0.

Silicon semiconductor diodes start allowing the current flow, if the voltage applied on the diode reaches 0.

Germanium semiconductor diodes do not allow the electric current flow, if the voltage applied on the germanium diode is less than 0. Germanium semiconductor diodes start allowing the current flow, if the voltage applied on the germanium diode reaches 0.

P–n junction

The cost of silicon semiconductors is low when compared with the germanium semiconductors. Advantages of p-n junction diode P-n junction diode is the simplest form of all the semiconductor devices. However, diodes plays a p n junction diode role in many electronic devices.

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A p-n junction diode can be used to convert the alternating current AC p n junction diode the direct current DC. The solid circles on the right of the junction represent the available electrons from the n-type dopant.

Near the junction, electrons diffuse across to combine with holes, creating a " depletion region ".

P–n junction - Wikipedia

The amount of minority diffusion in the near-neutral zones determines the amount of current that may flow through the diode. Only majority carriers electrons in n-type material p n junction diode holes in p-type can flow through a semiconductor for a macroscopic length. With this in mind, consider the flow of electrons across the junction.


The forward bias causes a force on the electrons pushing them from the N side toward the P side. With forward bias, the depletion region is narrow enough that electrons can cross the junction and inject into the p-type material.

However, they do not continue to flow through the p-type material indefinitely, because it is energetically favorable for them to p n junction diode with holes. The average length an electron travels through the p-type material before p n junction diode is called the diffusion length, and it is typically on the order of micrometers.

How a PN Junction Diode Works | Electronics Notes

P n junction diode total current the sum of the electron and hole currents is constant in space, because any variation would cause charge buildup over time this is Kirchhoff's current law. The flow of holes from the p-type region into the n-type region is exactly analogous to the flow of electrons from N to P electrons and holes swap roles and the signs of all currents and voltages are reversed.

Therefore, the macroscopic picture of the current flow through the diode involves electrons flowing through the p n junction diode region toward the junction, holes flowing through the p-type region in the opposite direction toward the junction, and the two species of carriers constantly recombining in the vicinity of the junction.

The electrons and holes travel in opposite directions, but they also have opposite charges, so the overall current is in the same direction on both sides of the diode, as required.