Diode or p-n Junction - Reverse Bias

When an external voltage V is applied across a semiconductor diode such that the p-type is connected to the -ve terminal and n-type to the +ve terminal of the battery (in general, p-type to low voltage and n-type to high voltage), the diode is said to be reverse biased.

\[V_{eff}=V_b+V\]

Where:

• \[V_b\]​ = potential barrier voltage
• \[V\] = applied external voltage

• In reverse bias, the current is quite small and is independent of the external voltage (until breakdown).
• The width of the depletion layer increases, and the p-n junction diode acts as a resistor.
• The width of the potential barrier increases, obstructing the flow of majority carriers in both the n-side and the p-side.
• In reverse bias, the majority charge carriers are attracted away from the depletion layer by their respective battery terminals connected to the p-n junction.
• Positive terminal attracts electrons away from the junction in the n-side; negative terminal attracts holes away from the junction in the p-side.
• Beyond a certain voltage, breakdown occurs via avalanche or Zener mechanism.