To get p-type semiconductor , impurity to be added to silicon should have wihich of the following number of valence electrons?

Options

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

Answer

To determine the number of valence electrons required for an impurity to be added to silicon in order to create a p-type semiconductor, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Structure of Silicon**:
- Silicon (Si) is a group 14 element and has 4 valence electrons. In its crystalline form, each silicon atom forms four covalent bonds with neighboring silicon atoms.

2. **Define Doping**:
- Doping is the process of adding impurities to a semiconductor to change its electrical properties. The type of doping determines whether the semiconductor will be n-type or p-type.

3. **Identify the Type of Semiconductor**:
- A p-type semiconductor is formed when the dopant creates "holes" in the silicon lattice. A hole is essentially the absence of an electron, which can carry a positive charge.

4. **Determine the Group of Dopants for P-type Semiconductors**:
- To create holes, we need to add an impurity that has fewer valence electrons than silicon. This means we should look for elements from group 13 of the periodic table, which have 3 valence electrons.

5. **Conclusion**:
- By adding a group 13 element (like boron, which has 3 valence electrons) to silicon, we create holes in the silicon lattice. Therefore, the number of valence electrons of the impurity to be added to silicon to achieve a p-type semiconductor is 3.

### Final Answer:
The impurity to be added to silicon to create a p-type semiconductor should have **3 valence electrons**.

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