The potential barrier existing across an unbiased p-n junction is 0.2 volt. What minium kinetic energy a hole should have to diffuse from the p - side to the n - side if (a) the junction is unbiased, (b) the junction is forward-biased at 0.1 volt and (c) the junction is reverse-biased at 0.1 volt ?

Options

A. 0.2 eV, 0.1 eV, 0.3 eV
B. 0.1 eV, 0.2 eV, 0.3 eV
C. 0.1 eV, 0.1 eV, 0.3 eV
D. 0.3 eV, 0.1 eV, 0.2 eV

Answer

To solve the problem, we need to determine the minimum kinetic energy a hole should have to diffuse from the p-side to the n-side of a p-n junction under three different conditions: unbiased, forward-biased, and reverse-biased.

### Step-by-Step Solution:

1. **Unbiased Junction:**
- The potential barrier across an unbiased p-n junction is given as 0.2 volts.
- For a hole to move from the p-side to the n-side, it must overcome this potential barrier.
- Therefore, the minimum kinetic energy (KE) required by the hole is equal to the potential barrier.
- **Calculation:**
\[ KE = \text{Potential Barrier} = 0.2 \, \text{eV} \]

2. **Forward-Biased Junction:**
- When the junction is forward-biased at 0.1 volts, the effective potential barrier is reduced.
- The new potential barrier can be calculated as:
\[ \text{Effective Barrier} = \text{Original Barrier} - \text{Forward Bias Voltage} = 0.2 \, \text{V} - 0.1 \, \text{V} = 0.1 \, \text{V} \]
- Therefore, the minimum kinetic energy required for the hole in this case is:
- **Calculation:**
\[ KE = 0.1 \, \text{eV} \]

3. **Reverse-Biased Junction:**
- When the junction is reverse-biased at 0.1 volts, the effective potential barrier increases.
- The new potential barrier can be calculated as:
\[ \text{Effective Barrier} = \text{Original Barrier} + \text{Reverse Bias Voltage} = 0.2 \, \text{V} + 0.1 \, \text{V} = 0.3 \, \text{V} \]
- Therefore, the minimum kinetic energy required for the hole in this case is:
- **Calculation:**
\[ KE = 0.3 \, \text{eV} \]

### Final Results:
- (a) Unbiased Junction: \( KE = 0.2 \, \text{eV} \)
- (b) Forward-Biased Junction: \( KE = 0.1 \, \text{eV} \)
- (c) Reverse-Biased Junction: \( KE = 0.3 \, \text{eV} \)

### Summary of Answers:
- (a) 0.2 eV
- (b) 0.1 eV
- (c) 0.3 eV