In a p-n junction diode the value of drift current through depletion region

Options

A. Decreases in forward biasing
B. Decreases in reverse biasing
C. Remains unchanged during forward or reverse biasing
D. Increases during reverse biasing

Answer

To determine the value of drift current through the depletion region in a p-n junction diode, we need to analyze the behavior of the diode under different biasing conditions. Here’s a step-by-step solution:

### Step 1: Understand the Structure of a p-n Junction
A p-n junction is formed by joining p-type and n-type semiconductors. The p-side has an abundance of holes (positive charge carriers), while the n-side has an abundance of electrons (negative charge carriers). When they are joined, electrons from the n-side and holes from the p-side recombine near the junction, creating a depletion region devoid of charge carriers.

**Hint:** Remember that the depletion region is formed due to the recombination of electrons and holes at the junction.

### Step 2: Analyze the Electric Field in the Depletion Region
The recombination of charge carriers leads to the establishment of an electric field across the depletion region. This electric field opposes the movement of charge carriers, leading to a drift current. The drift current is primarily due to the minority carriers in the p-type and n-type materials.

**Hint:** The electric field in the depletion region plays a crucial role in determining the direction and magnitude of the drift current.

### Step 3: Consider Forward Biasing
When the p-n junction is forward biased (the p-side is connected to the positive terminal of the battery and the n-side to the negative terminal), the applied voltage reduces the width of the depletion region. As the depletion region narrows, the electric field strength decreases, which in turn reduces the drift current.

**Hint:** In forward bias, the depletion region narrows, leading to a decrease in electric field strength and thus a decrease in drift current.

### Step 4: Consider Reverse Biasing
In reverse biasing (the p-side connected to the negative terminal and the n-side to the positive terminal), the depletion region widens. The electric field strength increases, but since the drift current is primarily due to minority carriers, the increase in the depletion width does not significantly increase the drift current. Instead, the drift current remains relatively constant, limited by the number of minority carriers.

**Hint:** In reverse bias, although the depletion region widens, the drift current does not increase significantly due to the limited number of minority carriers.

### Step 5: Conclusion
Based on the analysis:
- The drift current decreases during forward biasing due to the reduction in the depletion region and electric field strength.
- The drift current remains relatively unchanged during reverse biasing due to the limited number of minority carriers.

Thus, the correct answer is that the drift current through the depletion region **decreases in forward biasing**.

**Final Answer:** The value of drift current through the depletion region decreases in forward biasing.