Which of the following statements are true about semiconductors?

Options

A. Impurity of lower group creates n-type semiconductors
B. Impurity of higher group creates p-type semiconductors
C. Extrinsic semiconductors are formed by doping impurity
D. Intrinsic semiconductors become conductors when temperature is raised

Explanation

To determine which statements about semiconductors are true, we will analyze each statement one by one.

### Step-by-Step Solution:

1. **Statement A: Impurity of lower group creates n-type semiconductors.**
- **Analysis:** This statement is true. N-type semiconductors are created by doping a pure semiconductor (like silicon) with elements from group IV of the periodic table, such as phosphorus (which has five valence electrons). The extra electron from the dopant contributes to electrical conduction.
- **Conclusion:** True

2. **Statement B: Impurity of higher group creates p-type semiconductors.**
- **Analysis:** This statement is false. P-type semiconductors are formed by doping with elements from group III of the periodic table, such as boron (which has three valence electrons). These elements create "holes" in the semiconductor structure, which allows for conduction.
- **Conclusion:** False

3. **Statement C: Extrinsic semiconductors are formed by doping impurities.**
- **Analysis:** This statement is true. Extrinsic semiconductors are indeed formed by the intentional introduction of impurities (dopants) into a pure semiconductor to modify its electrical properties. The process of doping changes the conductivity of the semiconductor.
- **Conclusion:** True

4. **Statement D: Intrinsic semiconductors become conductors when temperature is raised.**
- **Analysis:** This statement is true. In intrinsic semiconductors, as the temperature increases, more electrons gain enough thermal energy to jump from the valence band to the conduction band, thus increasing the conductivity.
- **Conclusion:** True

### Final Assessment of Statements:
- **A:** True
- **B:** False
- **C:** True
- **D:** True

### Summary of True Statements:
The true statements about semiconductors are A, C, and D.

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