Forward Biasing in P-N Junction

When a P-N junction diode is forward biased, the P-side of the diode is connected to the positive terminal of the battery and the N-side is connected to the negative terminal. This creates a forward electric field that allows current to flow through the diode.

V-I Characteristics of a P-N Junction

The V-I characteristics of a P-N junction diode describe the relationship between the voltage applied across the diode (V) and the current flowing through the diode (I). It helps us understand how the diode behaves under different biasing conditions.

Regions in the V-I Characteristics

The V-I characteristics of a P-N junction diode can be divided into several regions:

1. Cut-off Region: In this region, the applied voltage is below the threshold voltage, and the diode behaves as an open circuit. The current is very low, close to zero.

2. Depletion Region: As the applied voltage increases above the threshold voltage, the diode enters the depletion region. In this region, the reverse biased P-N junction creates a potential barrier that prevents the flow of current. The current is still very low due to the narrow depletion region.

3. Forward Bias Region: Once the applied voltage exceeds the threshold voltage, the diode enters the forward bias region. In this region, the diode conducts current and the current increases rapidly with an increase in voltage.

4. Saturation Region: In this region, the diode is fully forward biased, and the current reaches its maximum value. The diode behaves as a short circuit, and the current remains constant even if the voltage is further increased.

5. Breakdown Region: If the applied voltage continues to increase beyond the saturation region, the diode enters the breakdown region. In this region, the diode breaks down and conducts a very large current, potentially damaging the diode.

Low Current Increase in the Depletion Region

In the depletion region, the current increase is very low during forward biasing. This is because the narrow depletion region limits the flow of majority carriers (electrons in the N-side and holes in the P-side) across the junction. The majority carriers have to overcome the potential barrier created by the reverse biased junction before they can contribute to the current.

As the forward bias voltage increases, the width of the depletion region decreases, allowing more majority carriers to cross the junction. This leads to an increase in current, but the increase is gradual due to the limited number of majority carriers available for conduction.

Therefore, the correct answer is option 'B' - Depletion Region.