Which of the following element is a donor impurity?

Options

A. Al
B. B
C. Ga
D. P

Answer

To solve the question "Which of the following element is a donor impurity?", we need to identify which element among the given options donates electrons when introduced into a semiconductor material.

### Step-by-Step Solution:

1. **Understanding Donor and Acceptor Impurities**:
- Donor impurities are elements that have more valence electrons than the semiconductor material (usually silicon, which has 4 valence electrons). These impurities donate extra electrons to the conduction band of the semiconductor.
- Acceptor impurities, on the other hand, have fewer valence electrons and accept electrons from the semiconductor, creating holes.

2. **Analyzing the Given Options**:
- The options provided are:
- A) Aluminium
- B) Boron
- C) Gallium
- D) Phosphorus

3. **Identifying the Valence Electrons**:
- **Aluminium (Al)**: Has 3 valence electrons (trivalent) - Acceptor impurity.
- **Boron (B)**: Has 3 valence electrons (trivalent) - Acceptor impurity.
- **Gallium (Ga)**: Has 3 valence electrons (trivalent) - Acceptor impurity.
- **Phosphorus (P)**: Has 5 valence electrons (pentavalent) - Donor impurity.

4. **Conclusion**:
- Among the options, only Phosphorus has more valence electrons than silicon and can donate an electron to the conduction band. Therefore, it is classified as a donor impurity.

5. **Final Answer**:
- The correct answer is **D) Phosphorus**.