to get a n- type semiconductor from silicon , it should be doped with a sustance with valency……….. .

Options

A. 2
B. 1
C. 3
D. 5

Explanation

To determine the valency of the substance that should be used to dope silicon in order to create an n-type semiconductor, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Silicon's Valency**:
- Silicon (Si) has 4 valence electrons. This means that in its crystalline structure, each silicon atom shares its 4 electrons with 4 neighboring silicon atoms, forming strong covalent bonds.

2. **Defining n-Type Semiconductor**:
- An n-type semiconductor is one that has an excess of electrons, which are the majority charge carriers. The "n" stands for negative, indicating that the charge carriers are negatively charged electrons.

3. **Doping with Higher Valency Element**:
- To create an n-type semiconductor, we need to introduce a dopant that has more valence electrons than silicon. This is because the dopant will provide additional electrons that can be freed to contribute to electrical conductivity.

4. **Evaluating the Options**:
- The options given are 2, 1, 3, and 5.
- If we consider each option:
- **Valency 2**: This would not provide enough electrons (less than 4).
- **Valency 1**: This also does not provide enough electrons (less than 4).
- **Valency 3**: This still does not provide enough electrons (less than 4).
- **Valency 5**: This would provide an extra electron (5 valence electrons), which is more than silicon's 4.

5. **Conclusion**:
- Therefore, to achieve an n-type semiconductor from silicon, it should be doped with a substance that has a valency of **5**. Elements from Group 15 of the periodic table, such as phosphorus (P), arsenic (As), or antimony (Sb), can be used as dopants.

### Final Answer:
To get an n-type semiconductor from silicon, it should be doped with a substance with valency **5**.

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