Semiconductors and their properties

Semiconductors are materials that have a conductivity between conductors (such as metals) and insulators (such as non-metals). They are an essential component in electronic devices, as they can be used to control the flow of electric current. Here are some key points about semiconductors:

1. Intrinsic and Extrinsic Semiconductors
Semiconductors can be classified as intrinsic or extrinsic based on their composition.

- Intrinsic Semiconductors: Intrinsic semiconductors are pure semiconducting materials, such as silicon (Si) or germanium (Ge). They have a specific crystal structure and their electrical properties are mainly determined by the temperature. At absolute zero temperature, intrinsic semiconductors behave as insulators because there are no free charge carriers. However, as the temperature increases, some electrons gain enough energy to break free from their atomic bonds and become free charge carriers, allowing for conduction.

- Extrinsic Semiconductors: Extrinsic semiconductors are impure semiconducting materials, where impurities are intentionally added to modify their electrical properties. This process is known as doping. Doping introduces additional charge carriers into the semiconductor, significantly altering its conductivity. Extrinsic semiconductors can be further classified as n-type and p-type.

2. Doping and Impurities
Doping is the process of intentionally adding impurities to a semiconductor material to modify its electrical properties. The impurities used in doping are typically atoms of other elements that have either more or fewer valence electrons than the atoms of the semiconductor.

3. n-type and p-type Semiconductors
Doping with impurities of different groups in the periodic table leads to the formation of n-type and p-type semiconductors.

- n-type Semiconductors: Doping a semiconductor with impurities from Group V elements, such as phosphorus (P) or arsenic (As), introduces additional negatively charged electrons into the crystal structure. These extra electrons become the majority charge carriers and are responsible for conduction in n-type semiconductors.

- p-type Semiconductors: Doping a semiconductor with impurities from Group III elements, such as boron (B) or gallium (Ga), introduces additional positively charged "holes" into the crystal structure. Holes are vacancies in the valence band where electrons can move to, creating a positive charge. These holes become the majority charge carriers and are responsible for conduction in p-type semiconductors.

4. Temperature and Conductivity
Intrinsic semiconductors, such as silicon or germanium, become better conductors as the temperature increases. This is because higher temperatures provide more thermal energy to the electrons, allowing them to break free from their atomic bonds and move more freely. However, it's important to note that intrinsic semiconductors never become as conductive as metals, even at high temperatures.

Conclusion
In summary, the true statement about semiconductors is that intrinsic semiconductors become conductors when the temperature is raised (option D). This is due to the increase in thermal energy, which allows some electrons to break free from their atomic bonds and contribute to conduction. Extrinsic semiconductors, on the other hand,