If a small amount of antimony is added to germanium crystal

Options

A. its resistance is increased
B. it becomes a p-type semiconductor
C. there will be more free electrons than holes in the semiconductor
D. none of these

Explanation

To solve the question regarding the effect of adding a small amount of antimony to a germanium crystal, we can break down the explanation into clear steps:

### Step-by-Step Solution:

1. **Understanding the Nature of Germanium**:
- Germanium (Ge) is a tetravalent semiconductor, meaning it has four electrons in its outermost shell. This allows it to form covalent bonds with four neighboring germanium atoms.

2. **Introducing Antimony**:
- Antimony (Sb) is a pentavalent element, which means it has five electrons in its outermost shell. When a small amount of antimony is added to germanium, it acts as a dopant.

3. **Covalent Bond Formation**:
- In the germanium crystal, the antimony atom will form covalent bonds with four neighboring germanium atoms using four of its five electrons. This leaves one extra electron from the antimony atom that is not involved in bonding.

4. **Free Electrons and Holes**:
- The extra electron from the antimony becomes a free electron, contributing to electrical conduction. Therefore, in this case, there will be more free electrons than holes in the semiconductor.

5. **Type of Semiconductor Formed**:
- Since the addition of antimony (a pentavalent impurity) results in an increase in free electrons, the semiconductor becomes an n-type semiconductor. This is characterized by an abundance of negative charge carriers (electrons).

6. **Conductivity Changes**:
- The conductivity of the extrinsic semiconductor (doped with antimony) will be higher than that of intrinsic germanium due to the increased number of charge carriers (free electrons).

7. **Conclusion**:
- Therefore, adding a small amount of antimony to a germanium crystal increases its conductivity and transforms it into an n-type semiconductor.

### Final Answer:
The correct conclusion is that adding a small amount of antimony to germanium results in the formation of an n-type semiconductor with increased conductivity.

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