*Question E6A04:
What is the name given to an impurity atom that adds holes to a semiconductor crystal structure?*  

*Correct Answer is  C: Acceptor impurity*  

### AI Response: (may contain errors)  

The correct answer to the question is **C: Acceptor impurity**. 

### Explanation:

1. **Why the correct answer is correct:**
   - An **acceptor impurity** is an atom that, when added to a semiconductor, creates "holes" in the crystal structure. These holes are essentially places where an electron is missing, allowing for the conduction of electricity. Acceptor impurities typically come from elements in group III of the periodic table, such as boron or aluminum, which have fewer valence electrons than silicon (which has four). When these atoms are introduced into the silicon lattice, they accept electrons, creating holes that can carry positive charge.

2. **Why the other choices are incorrect:**
   - **A: Insulator impurity**: This term is not commonly used in semiconductor physics. Insulators do not conduct electricity and do not create holes or free electrons in the semiconductor.
   - **B: N-type impurity**: N-type impurities are elements from group V of the periodic table, such as phosphorus or arsenic, which donate extra electrons to the semiconductor, increasing the number of free electrons rather than creating holes.
   - **D: Donor impurity**: Similar to N-type impurities, donor impurities provide additional electrons to the semiconductor. They do not create holes; instead, they enhance the negative charge carrier concentration.

### Useful Concepts:
- **Semiconductor Doping**: The process of adding impurities to a semiconductor to change its electrical properties.
  - **Acceptor impurities** create holes (positive charge carriers).
  - **Donor impurities** provide extra electrons (negative charge carriers).

Understanding these concepts is crucial for grasping how semiconductors function in various electronic applications.