Which of the following statements is true for an n-type semi-comductor?

Options

A. the donor level lies closely below the bottom of the conduction band
B. the donor level lies closely above the top of the valence band
C. the donor level lies at the halfway mark of the forbidden energy gap
D. none of the above

Explanation

To determine which statement is true for an n-type semiconductor, we can analyze the characteristics and properties of n-type semiconductors step by step.

### Step-by-Step Solution:

1. **Understanding n-type Semiconductors**:
- An n-type semiconductor is created by doping a pure semiconductor (like silicon) with a group V element (like phosphorus or antimony). These elements have five valence electrons, which means they provide extra electrons to the semiconductor.

2. **Donor Levels**:
- In n-type semiconductors, the dopant atoms create energy levels known as donor levels. These levels are associated with the extra electrons provided by the dopant atoms.

3. **Location of Donor Levels**:
- The donor levels are situated just below the conduction band of the semiconductor. This means that the energy required for the extra electrons to jump into the conduction band is relatively small.

4. **Energy Band Diagram**:
- In an energy band diagram, the conduction band is at a higher energy level than the valence band. The donor level is positioned just below the conduction band, allowing the extra electrons to easily transition into the conduction band at room temperature.

5. **Conclusion**:
- Based on this understanding, the statement that is true for an n-type semiconductor is that the donor level lies closely below the bottom of the conduction band.

### Final Answer:
The correct statement for an n-type semiconductor is: **The donor level lies closely below the bottom of the conduction band.**

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