To learn about forward and reverse biasing of a p-n junction diode, let’s break down the concept step by step:
• When a p-n junction is formed, electrons from the n-side combine with holes from the p-side, creating a depletion region where no free charge carriers exist.
• This forms a barrier potential, stopping current flow unless an external voltage is applied.
• Definition: When the p-side (positive) is connected to the positive terminal of a DC power supply and the n-side (negative) is connected to the negative terminal of the supply.
• Mechanism:
The negative terminal pushes electrons from the n-side towards the junction, and the positive terminal pushes holes from the p-side towards the junction.
This reduces the width of the depletion region.
As the barrier potential decreases, more charge carriers (electrons and holes) cross the junction, allowing a large current to flow.
When the external voltage exceeds the barrier potential, the depletion region collapses, further enabling current flow.
• Definition: When the p-side is connected to the negative terminal of a DC power supply and the n-side is connected to the positive terminal.
• Mechanism:
Electrons in the n-region are attracted to the positive terminal, and holes in the p-region move towards the negative terminal.
This causes an increase in the width of the depletion region, increasing the barrier potential.
As a result, current flow through the junction is blocked except for a tiny leakage current due to minority carriers.
No steady current flow is observed, as there is no continuous movement of charge carriers across the junction.